Morphologic and Biologic Characteristics of the Canine Cutaneous Histiocytoma'

[CANCER RESEARCH 29, 83â€”92,January 1969]

Dee 0. N. Taylor, C. Richard Dorn, and Osman H. Luis

Viral and Rickettsial Disease Laboratory, California State Department ofPublic Health, Berkeley, California 94 704

SUMMARY term histiocytoma with transmissible venereal tumor. How ever, they pointed out that, while cells of typical transmissible Five hundred and twenty canine cutaneous histiocytomas venereal tumors (those found on the external genitalia) con (CCH) that developed in the dog population of Alameda and tam only 59 chromosomes, cells of â€œextragenitalvenereal tu Contra Costa Counties, California, during 3 years were col morsâ€• contain 76 chromosomes, the usual number for normal lected. Morphologic studies confirmed the noninvasive charac dog cells. ter of the tumors and the proliferative histiocytic nature of the Moulton ( 15) categorizes such extragenital tumors as canine cells. The average annual incidence rate during the 3-year per cutaneous histiocytomas (CCH) and considers them to com iod was 117 per 100,000 dogs. Although the CCH occurred prise a distinct entity which is â€œclearlydistinguishable from over most of the body, a high proportion were found on the the usual forms of mastocytoma, fibroma, and reticulum cell head. Boxers and dachshunds had a significantly higher risk sarcoma, andâ€”despite claims to the contraryâ€”is morpholog than all other breeds, and purebred dogs in general had a high ically distinct from transmissible venereal tumor of the dog.â€• er risk than crossbred dogs. A followup study of 230 cases The above views were based primarily on the morphologic -indicated that CCH rarely recur at the site of excision, at a characteristics of such tumors. Therefore, this project was un new site, or at 2 sites simultaneously. Widespread metastases dertaken to investigate the biologic and epizootiologic charac or death as a result of CCH were not observed. Efforts to teristics of a large series of skin tumors conforming to transmit this tumor to dogs and hamsters were unsuccessful as Moulton's criteria for CCH and to gain additional information were attempts to detect viruses, bacteria, or fungi as etiologic regarding their morphologic features. agents. The findings of this study help to establish the CCH as a distinct entity and make it possible to differentiate it from MATERIALS AND METHODS various mesodermal neoplasms on the basis of morphologic, biologic, and epizootiologic characteristics. Neoplasms. Formalin-fixed specimens of the CCH were re ceived through an animal neoplasm registry (ANR) in Alameda INTRODUCTION and Contra Costa Counties, California (3, 4). Fresh specimens of the CCH were acquired from veterinary practitioners who Perhaps the earliest utilization of the term histiocytoma in notified the ANR by telephone when an animal with a suspec reference to benign mesenchymal tumors in the skin of dogs ted CCH was presented at their hospitals. The specimens were was by Mulligan in 1948 (18). He later concluded that such collected aseptically, and portions were placed in tissue culture tumors were identical to venereal lymphosarcoma (19). media, a dry vial, and/or 4.5% glutaraldehyde and transported Prior to this, similar tumors in the skin of dogs had been to the laboratory at 4Â°Cwithin 1 hour of the time of excision. referred to as round cell sarcomas (14) or transmissible Light microscopy. Fifty specimens of CCH were selected for lymphosarcomas (10). special light microscopic studies using tungsten, ultraviolet, About the same time as Mulligan's report appeared, Ottosen and polarized light sources. Both phase and bright-field optics (21) reported on 201 skin neoplasms of dogs of which he were used. Hematoxylin and eosin, Dominici's mast cell, Ziehl considered 67 to be reticulosarcomata. With the exception of Nielsen acid fast, Geimsa's, Gridley's fungus, Masson's one large neoplasm which metastasized, the description of trichome, Gordon and Sweet's reticulum, Mallory's iron, the these tumors seems compatible with Mulligan's description of periodic acid-Schiff (PAS), oil red 0, 3,4-benzpyrene (22), and histiocytoma. More recently, Orkin and Schwartzman (20) re acridine orange (1) staining procedures2 were applied to ap ferred to such skin tumors as transmissible reticulum cell sar propriate frozen or paraffin-embedded sections, impression comas and considered this term synonymous with transmis smears, and cell cultures in order to define the histologic fea sible venereal tumor. tures. Like Mulligan (19), Smith and Jones (26) associated the 2@jI staining methodswith exception of the 3,4-benzpyreneand â€˜This study was supported by Research Grants CA-05924 and CA acridine orange stains were according to the Manual of Histologic and 07730 from the National Cancer Institute, NIH, U. S. Department of Special Staining Technics, from the Armed Forces Institute of Path Health, Education and Welfare, Bethesda, Md. ology, Ed. 2, New York, Blakiston Division, McGraw-Hill Book Co., Received April 8, 1968; accepted September 12, 1968. Inc., 1960.

JANUARY 1969 83

Mitotic indexes were calculated as the number of mitotic Earle's BSS were added to these cultures with 10% fetal bovine figures per 1000 cells. This was accomplished by placing a grid, serum. to facilitate counting, in the light path of a photomicrographic Virus Isolation Attempts. Cell fragments of 10 CCH were system so that the image of the grid was superimposed over inoculated into 6 test tube cultures of each of the DK cell line, randomly selected microscopic fields of stained sections. These secondary dog kidney cells, hamster fetal kidney cells, and microscopic fields were magnified 312 times by the micro hamster fetal lung cells. Each culture was examined twice scope and photographically enlarged to 935 magnifications. weekly for cytopathic effects by comparing it to uninoculated controls. At 2-week intervals, all the cultures were frozen and Epizootiologic Studies. Five hundred and twenty cases of thawed, and 0.2 ml of the resulting suspension of cellular de CCH were reported to the ANR between July 1963 and June bris was inoculated onto fresh cultures; 3 blind passages were 1966. Two hundred and eighty cases were from Alameda made in this manner. county and 240 cases were from Contra Costa County. Popu Ten CCH were tested for the presence of noncytopathic lation data, to serve as denominators and comparison groups agents that would interfere with subsequent infection by the (controls),wereavailableonlyforAlamedaCounty(5).There infectious canine hepatitis virus. Ground tissue from each spec fore, estimates of age-specific incidence rates and relative risk imen was frozen and thawed, then incubated with cells of the estimates (13) were obtained using the 280 cases from this DK cell line in Petri dishes for 1 hour. The cultures were county. A special followup study was conducted on 230 CCH washed; then, along with untreated parallel cultures, they were collected from both counties during July 1963 through March inoculated with serial dilutions of the infectious canine hepa 1965, to determine the number of recurrences or metastases titis virus. Three cultures were used for each virus dilution. that had occurred. Letters were sent to the veterinarians at After 0.5 hour incubation, the cultures were overlayed with tending each case to request current information about the agar. Five days later the cultures were stained with 1:20,000 involved animals. Cards with appropriate followup questions neutral red, and the numbers of plaques were counted to de and stamped, self-addressed envelopes were enclosed to facii termine if there was interference of plaque formation in cul tate the collection of information. Personal visits and tele tures treated with tumor extracts. Cultures treated with tumor phone calls by a staff member were used to attain 100% return extracts but not inoculated with the virus served as controls to of the cards. detect cytopathology induced by the tumor extract. Cell Cultures. Secondary dog kidney cell cultures were ob Transmission Trials. Attempts to transmit 24 CCH were tamed by trypsinization of day-old puppy kidneys. Primary made in 30 young dogs and 11 fetuses. Viable trypsinized cultures were initiated by inoculating 8-oz. prescription bottles cells, explants, or cell fragments that had been ground, then with 10 ml of a 1:200 cell suspension in medium 199 in frozen and thawed, were inoculated by subcutaneous or intra Earle's balanced salt solution (BSS) and 10% fetal bovine dermal routes into young dogs. Trypsinized cells or explants serum. Following the initial outgrowth, secondary cultures were inoculated into young dogs by the intraocular route and were made by inoculating 200,000 cells from trypsinized pri into fetuses by intracranial and subcutaneous routes in order mary cultures into test tubes in 1.0 ml of the above medium. to place viable cells in immunologically privileged sites. After monolayers had formed, the cultures were inoculated Forty-two weanling hamsters were inoculated in the cheek with the test material and maintained with 2.0 ml of medium pouch with trypsinized cells or explants from 5 different his 199 in Earle's BSS and 5% fetal bovine serum. Incubation was tiocytomas. Each hamster was injected twice weekly with 2 at 36Â°C in stationary racks; medium changes were made twice mg of cortisone as an immunodepressant. a week. Fetal hamster lung and kidney cell cultures were prepared in RESULTS the same manner, except that trypsinized cells were seeded directly into test tubes, and Eagle's medium in Earle's BSS Gross Morphology. When seen by practicing veterinarians, with 10% fetal bovine serum was used for outgrowth and dogs with CCH usually had a circular dome-shaped lesion in maintenance. These cultures were used in the primary passage. the skin, which had developed rapidly and ulcerated early, A continuous dog kidney (DK) cell line was acquired from causing little or no discomfort. The surface was covered with Dr. A. H. Fieldsteel, Stanford Research Institute, Palo Alto, thin shiny or ulcerated epidermis through which sparse hairs California. These cells were used from the 121st through the projected (Figs. 1â€”4). Erythema of this semiglabrous surface 145th passage, and test tube cultures were prepared in the prompted the colloqually-used synonym â€œstrawberry tumor.â€• same manner as the secondary dog kidney cells. In addition, The lesions varied from 0.5 to 4.0 cm in diameter with the 60-mm plastic Petri dishes were seeded with a 4.0 ml of a majority being 1.0 to 2.0 cm@ The height that these tumors 1:200 dilution of cells and incubated in 5% humidified CO2 at rose above the surface of the skin was usually less than 50% of 36Â°C when the cells were to be used in virus interference tests. the diameter (Figs. 3â€”5). Upon cutting, fresh CCH had a

â€˜ Fresh CCH tissue was trypsinized and cell suspensions were rather pliable but tough and resilient consistency. The cut sur placed in test tubes. Other specimens of fresh CCH were cut face of fresh tissue bulged slightly and was nearly white with into explants and attached to the walls of the test tubes or varying light shades of yellow (Fig. 4). On cross section the round coverslips, 15 mm in diameter, with chicken plasma deep margins of the tumors were well def'med but not encap clots. The coverslips were placed in 60-mm plastic petri dishes. sulated. These margins described arcs varying from nearly flat Rose chamber preparations (25) were also made. Puck's mcdi to a crude half-circle extending for various depths into the um V-16, medium 199 in Earle's BSS, or Eagle's medium in subcutis (Figs. 4, 5).

84 CANCER RESEARCH VOL.29

Microscopic Studies. Sections of nonulcerated CCH ap Often they were sparse, providing the impression that they peared as uniform sheets of cells which infiltrated the dermis were derived from preexisting dermal connective tissue which and subcutis causing the collagenous fibers and skin adnexia to had been spread apart by the tumor cells (Fig. 11). appear rather widely dispersed (Fig. 5). Along the deep mar Reticulum fibers were more numerous, and they segregated gins, fat vacuoles were trapped and the tumor cells compressed the cells into packets varying from 1 to more than 20 cells and infiltrated the subjacent connective tissue (Fig. 5). Super (Fig. 12). ficially, the tumor cells were occasionally compressed against Incidence. Of 4,842 canine neoplasm cases reported to the the overlying epidermis, but more often there were interstitial ANR during the period July 1963 to June 1966, 520 (10.7%) spaces causing cells in the subepithelial region to appear mdi were diagnosed as CCH. The average annual incidence rate was vidually discrete (Fig. 6). Most commonly there was ulceration 116.7 per 100,000 dogs in Alameda County (Table 1). of the overlying epidermis, and the superficial tumor cells were There were more CCH cases observed among male dogs than mixed with inflammatory exudate (Fig. 7). expected; however, the difference in relative risk as compared The cells comprising these tumors had many features com to female dogs was not statistically significant (Table 2). Like patible with Porter's (23) description of histiocytes (macro wise, there was no significant difference in risk between intact phages). This was apparent in smears and tissue culture prepa and neutered female dogs. The relative risk of developing CCH rations where flattened individual cells were available for by neutered and intact male dogs was not computed due to study. In smears, the cells had round to oval or indented nuclei the small number of neutered male dogs in case and control which were nearly twice the diameter oflymphocytes (Fig. 8). groups. Usually one or more nucleoli were discernible, and the nuclear Purebred dogs had a higher risk of developing CCH than chromatin was finely particulate and evenly dispersed. The crossbred dogs (Table 2). Among dog breeds tested by com cytoplasm was faintly acidophilic, and vacuolated or granular, paring their risk with that of appropriate comparison groups of with indistinct limiting membranes (Fig. 8). In tissue culture all other purebred dogs, boxer and dachshund dogs had excess preparations, the nuclei were more uniformly oval and multi risks which were statistically significant. The poodle breed had plc nucleoli were prominent. The cytoplasm was voluminous a signfficantly lower risk of CCH. and vacuolated, with indistinct limiting membranes (Fig. 9). In sections of paraffin-embedded tissue, the tumor cells were slightly larger than neutrophils (Fig. 7). Where cells were tight Table 1 ly packed, cytoplasmic membranes were indistinct (Fig. 10), neoplasmsNumberbenignkin but they became more apparent and rounded when separated Age Number of Rate per of per (years)Histiocytoma cases 100,000Other by intercellular spaces (Figs. 6, 7). The cytoplasm was faintly 100,000Allages casesRate acidophiic, rather abundant, and granular (Fig. 10). The nu 40.22-362109.23968.74-52351.775168.76-71885.0120566.58-91695.51681002.310-11656.01571465.912-13445.21741966.714Lessthan2280 149116.7 214.1843 28351.2 dci were pleomorphic, being round or oval to indented, and the nuclear chromatin was rather scant and distributed as fine particles and filaments, with aggregates often distributed along the well-defined nuclear membrane (Fig. 10). About 73% of the cells had a single visible nucleolus and 9% had multiple nucleoli. and over240.9821675.8 A distinctive feature of this tumor was its high mitotic in Numbers of cases and age-specific incidence rates for the canine cutaneous dcx. Individual counts from 15 randomly selected CCH ranged histiocytoma and other benign skin neoplasms of dogs, Alameda County, from 2.4 to 8.7 mitotic figures per 1000 tumor cells with an July 1963â€”June 1966. Rates are per 100,000 dogs. average count of 5.5. With ulcerated CCH the epidermis had sloughed, and necrot ic tumor tissue, infiltrated by purulent inflammatory exudate, The age-specific incidence rates for CCH were markedly dif was present on the surface. The deep margins of ulcerated ferent than the rates for other benign skin neoplasms (Table CCH were usually infiltrated by lymphocytes, plasma cells, 1), being low at older ages and extremely high at younger ages; and small numbers of neutrophils. Such tumors often con approximately 50% of the CCH occurred before the age of 2 tamed small foci of coagulation necrosis which were also infil years. trated by lymphocytes plus varying numbers of neutrophils. Acquisition of cases was nearly constant throughout the 3 Small granules of PAS-positive material were present in and study years, indicating no seasonal variations in incidence. around areas of necrosis, but they were not seen in viable Sites. All of the CCH were located in the skin. They were tumor cells. These granules were not digested by diastase. most commonly found on the head (152 of 520, or 29%) Dominici's or Geimsa's stains did not demonstrate cyto (Chart 1). Seventy-two or nearly one-half of those on the head plasmic metachromatic granules except in mast cells, which were located on the pinna of the ear. The remainder were were usually present in small numbers in and around some distributed over the neck, limbs, trunk, and tail. tumors. Course of the Disease. In the followup study of 230 cases of Detectable lipid was not present in tumor cells of frozen CCH that were submitted to the ANR from July 1963 through sections of formalin-ffxed or fresh CCH tissue stained by the March 1965, adequate information was available on 204. Al oil red 0 or 3,4-benzpyrene methods. though responses were acquired on all the cases, in 26 in The collagen fibers in these tumors were variable in amount. stances information was inadequate because owners left the

JANUARY 1969 85

2Study Table

groupObservedGExpectedbRcx2cSexMale(vsfemale)151139.441.252.21Intact

female)7581.921.402.05BreedPurebredfemale (vs neutered

crossbred)195179.821.404â€¢61dPoodle(vs purebred)2844.260.4710â€¢22dCocker(vs all other purebred)77.980.820.04GermanSpaniel (vs all other Shepherd (vs all other purebred) Chihuahua3.38Dachshund (vs all other purebred)11 716.92 12.970.55 0.452.69 purebred)2716.652.369â€¢02dBoxer(vs all other purebred)167.174.9413â€¢96dBoston(vs all other Terrier (vs all other purebred)116.600.103.26 Estimated relative risks (R) of canine cutaneous histiocytomas for selected sex and breed categories, Alameda County, California, July 1963â€”June 1966. aThe observed numbers were cases in the study group. bThe expected numbers were based on the combination of the study group and the comparison group, age, sex, and neutering among females were control factors in all comparisons, except when neutering was the test factor. CThe X2 (df = 1) and R values were computed using the Mantel-Haenszel procedure (13). dstatistically significant at the 5% level or less. area or failed to communicate with the attending veterinarian. specimens. No bacteria were seen in specimens where the over At the completion of the followup study in July 1956, 196 of lying epidermis was intact, and the Gridley stain for fungi these CCH had not recurred or metastasized. In one case CCH failed to reveal mycotic elements. had arisen simultaneously at 2 sites on the same dog without Cell Cultures. Attempts to grow the cells of CCH in various recurrence or metastasis following excision. The attending vet cell culture systems had limited success. Trypsinization of erinarians knew of 7 deaths. Six of the deaths were known to CCH yielded very small numbers of cells, not only because of be from causes other than neoplasia. The one dog that died of the small size of the tumors, but also due to the ineffectiveness an unknown cause had ascites and recurrence of a tumor at the of trypsin in dispersing the cells. Cultures of trypsinized cells site of removal of a CCH. This dog was not made available for required 2 to 3 weeks for significant growth to develop, and necropsy. the resulting cells were of a fibroblastic type. Of the 197 dogs alive at the end of the followup study, 5 A few histiocytic cells began migrating from explants within had acquired additional tumors. Four of these were in the skin 48 hours of explantation. These cells were evident for as many and one involved the iris of the eye. Subsequent submissions as 3 passages (Fig. 9). Foci of squamous epithelial cells (appar of the skin tumors from 3 of these dogs were found to be ently derived from hair follicles, since the surface epithelium benign neoplasms other than CCH plus 2 epidermal cysts. The was trimmed away from the explants) persisted for as many as fourth dog had a recurrence of CCH on the same ear from 8 passages, although all the cultures eventually became fibro which a CCH was previously removed. The tumor from the eye blastic. Of a total of 25 CCH subjected to tissue culture was not made available for examination. methods, 12 were maintained for 5â€”9passages, 4 for 10â€”14 Anamestic data subsequently submitted to the ANR mdi passages, and 1 for 1 5 passages. cated that of the total 520 cases of CCH in this study, there Transmission Studies. No evidence of cellular proliferation was 1 additional instance when 2 CCH arose simultaneously on was seen during attempts to transmit the CCH to 30 young the same dog. Recurrences occurred at the site of excision in 3 dogs and 1 1 fetuses. Explants could be found in the brains of cases, and CCH arose at new sites following surgery in 3 cases. dogs that died during the first week of life following intra In 1 instance, a CCH was reported to have regressed during a cranial inoculation as fetuses. The neoplastic cells were under 2-week period following biopsy. There were no reports of gen going coagulation necrosis at that time with little inflamma eralized metastasis or death due to the direct effects of CCH. tory response or necrosis in the surrounding brain tissue (Fig. Microbiologic Studies. No cytopathic agents were isolated 13). The dogs that survived for extended periods of time did during 3 blind passages of 10 specimens of ground CCH tissue not develop neurologic abnormalities. Explants inoculated into in cell cultures of the DK cell line, secondary dog kidney, dogs by the intraocular route persisted for several months, but hamster fetal lung, or hamster fetal kidney. there was a gradual reduction in size until the only residual Noncytopathic agents were not detected where 10 specimens effect was a small corneal opacity where the needle had been of ground CCH were inoculated onto DK cells in search of an inserted. Suspended cells were dissipated more rapidly than agent that would interfere with subsequent infection of the explants. Dogs inoculated intradermally or subcutaneously did same cells by the infectious canine hepatitis virus. not exhibit any noticeable reaction. In sections from paraffin-embedded tissues of 50 CCH, No neoplastic growths were observed in the cheek pouches staphylococcal organisms could be seen in the surface exudate of the 42 hamsters inoculated with explants or trypsinized of most of the ulcerated specimens. Occasionally Gram CCH cells. Some of the explants were visible for longer than 2 positive bacilli could also be seen near the surface of ulcerated months, but there was a gradual reduction in size. Histologic

86 CANCER RESEARCH VOL.29

Downloaded from cancerres.aacrjournals.org on October 1, 2021. © 1969 American Association for Cancer Research. Canine Cutaneous Histiocytoma examination of the cheek pouches revealed small clumps of Therefore, the cytologic similarity between the cells of the degenerating collagen fibers embedded in the subepithelial CCH and transmissible venereal tumor seems to be the prin connective tissue. The inflammatory reactions at these sites cipal reason for difficulty in distinguishing the two. Even at were negligible. this level, however, significant differences have been detected. Jackson (8) reported the presence of lipid droplets in the DISCUSSION cytoplasm of cells of transmissible venereal tumors. Lipid was not evident in the cytoplasm of cells making up CCH in 50 It is apparent from previous work that lesions typical of cases that were examined specifically for this characteristic. CCH have been categorized with other neoplasms, principally Also, Smith and Jones (26) cited works which reported a dif the transmissible venereal tumor (19, 26), as well as lympho ference in the numbers of chromosomes in cells making up the sarcoma (10) and reticulum cell sarcoma (20, 21). transmissible venereal tumor and lesions similar to CCH. The lack of identity of the CCH with the transmissible vene The mesodermal appearance of cells of the CCH may make it real tumor can be established on the grounds of morphology, difficult to differentiate from malignant neoplasms such as biologic activity, and epizootiologic characteristics. The CCH lymphosarcoma. However, this and related terms are inappro is smaller than most transmissible venereal tumors and in our priate since CCH cells are not of the lymphocytic series, as can study was found only in the skin. In agreement with Lacroix be demonstrated by their morphologic and tinctorial qualities; and Riser (10), the head, and more specifically the ear, was a particularly in cell cultures and smears (Figs. 8, 9). definite site of predilection for CCH (Chart 1). In examining sections of paraffin-embedded tissue stained by Conversely, transmissible venereal tumors have been most routine methods, the reticulum cell appears to be a likely often associated with the mucous membranes of the penis, progenitor of the CCH, as indicated by application of terms prepuce, and vagina (26). They originate as nodular or papil such as reticulosarcoma (21), and transmissible reticulum cell lary proliferations which may progress to large friable cauli sarcoma (20) to neoplasms that had the characteristics of flower-like masses (17). In this series only 3 CCH were asso CCH. Moulton contends (16) that reticulum fibers are inti dated with the external genitalia. These were in the skin of the mately associated with individual cells in reticulum cell sar prepuce. Only 5 typical transmissible venereal tumors were coma. Other authors (1 1, 24) contend that reticulum cells vary seen among the 4,842 neoplasms in this series. Four involved in their ability to produce fibers. In this study it was doubtful the mucous membranes of the penis and/or prepuce and 1 the that the cells of CCH played a role in the production of reticu mucous membrane of the vagina. It is of interest to note that 4 hun fibers (Fig. 12). This, plus the fact that the reticulum cell of these dogs had been brought to California from Texas, sarcoma generally is considered a part of the highly fatal ma Louisiana, Costa Rica, or Guam a short time prior to the sur lignant lymphoma group (11, 24), should discourage applica gery. Only 1 dog had lived in California all of its life. This tion of the term reticulum cell sarcoma to neoplasms with the would indicate that the transmissible venereal tumor is rare in characteristics of CCH. California and thus segregates it from the CCH on an epi There is also difficulty in distinguishing CCH from small zootiologic basis. mast cell tumors (2). Careful and routine application of In 520 cases of CCH, multiple sites of involvement, recur Geimsa's stain or procedures employing toluidine blue, such as rences at the site of excision, and reports of spontaneous re Dominici's stain, are very useful in differentiating between the gressions were rare. Metastases or death due to direct effects of two. CCH were not observed. On the other hand, transmissible Considering the histiocytoma of the skin of man (12), there venereal tumors frequently regress spontaneously and metas is evidence that these are related to injury since they are usu tases have been reported (17, 26). ally associated with considerable blood and/or blood pigments. As denoted by its name, the transmissible venereal tumor Some contain numerous vascular channels, and fibrous connec may be readily transmitted between dogs. Forty-one attempts tive tissue is a major component. The histiocytes may contain to transmit the CCH between dogs failed. lipid (xanthomas) (12). Histopathologic differentiation be tween these and CCH is possible, based on the paucity of Face& Scalp 38.8 fibrous connective tissue, vascular channels, blood pigments, EyeLid and lipid in CCH. Therefore, while the term histiocytoma Nose of Sites lip 24Pinna Eor(72)Other onljeod(80) seems as applicable to these benign canine tumors as other terms, it is important to qualify it as â€œcaninecutaneous histio Nock 48 cytomaâ€• in order to clearly separate it from other specific entities. FrontLegs 11 [email protected] l@. The CCH occurred with high incidence in the population studied, involving approximately 1 17 dogs per 100,000 per Nommoe year and comprising 17.9% of the skin neoplasms. These re Peridnolâ€˜2 suits are similar to those of other reports (9, 10, 14, 20) which Toil â€˜5 Unspecified indicated that neoplasms of this and similar types occur among sb iÃ´o @rsoskin-associatedneoplasmswith frequenciesrangingfrom 17% to 33%. NUMBER In this study approximately 50% of the CCH occurred in Chart 1. Topographic distribution of canine cutaneous histiocytomas. dogs before they became 2 years of age (Table 1). This is in

JANUARY 1969 87

Downloaded from cancerres.aacrjournals.org on October 1, 2021. © 1969 American Association for Cancer Research. Dee a N. Taylor, C'.Richard Dorn, and Osman H. Luis agreement with Head (6), whose data indicated that the mean County, California, 1965. California State Department of Public age for the occurrence of histiocytomas of dogs was 2.7 years. Health, Berkeley, 37 pp., 1967. Therefore, age is a useful criterion in differentiating this tumor 6. Head, K. W. The Application of Biopsy Technique to Accessible from neoplasms such as lymphosarcoma or reticulum cell sar Tumors in Small-Animal Practice. Proc. Brit. Sm. Animal Vet. Assoc. Cong., 1: 55â€”64, 1950. coma, where the most frequent age of occurrence is over 8 7. Howard, E. B., and Nielesen, S. W. Neoplasia of the Boxer Dog. years (4). Am. J. Vet. Res., 26: 1121â€”1131, 1965. The results of this study indicate that purebred dogs have a 8. Jackson, C. The Cytology of the Contagious (Venereal) Tumor of higher risk of developing CCH than crossbred dogs. Among the Dog. Onderstepoort J. Vet. Sci. and Animal Industry, 20: breeds tested the boxer had the greatest risk of CCH (Table 2); 97â€”118, 1944. this is also true with some other forms of neoplastic disease 9. Jubb, K. V. F. and Kennedy, P. C. The Skin and Appendages. In: (7). Dachshunds also had an excess risk of CCH, and poodles Pathology of Domestic Animals., Vol. 2, pp. 570â€”571. New York: apparently had a reduced risk, indicating that genetic factors Academic Press, 1963. regarding breed may also play a role in the development of 10. Lacroix, J. V. and Riser, W. H. Transmissible Lymphosarcoma of CCH. the Dog. North Am. Vet., 28: 451â€”453,1947. It has been suggested that the CCH might be a peculiar type 11. Lever, W. F. Lymphoma and Myelosis. In: Histopathology of the Skin, Ed. 3, pp. 605â€”606. Philadelphia: J. B. Lippincott Co., 1961. of inflammation (15). In spite of ample opportunities for an 12. Lund, H. Z. Tumors of the Skin. Subcommittee on Oncology of etiologic agent to become manifest through virus isolation the Committee on Pathology of the National Research Council, technics, histiologic examination for bacteria and fungi, and Armed Forces Institute of Pathology, Washington, D. C., Section I, animal inoculation with tumor cells; no evidence of a specific Fasicle 2, pp. 274â€”275,1957. infectious and/or oncogenic agent was detected. 13. Mantel, N. and Haenszel, W. Statistical Aspects of the Analysis of The rapid proliferation of histiocytic cells in CCH, without Data from Retrospective Studies of Disease. J. Natl. Cancer Inst., the stimulus of a defined etiologic agent, supports the interpre 22: 719â€”748,1959. tations of others that they are benign neoplasms which arise de 14. McClelland, R. B. Neoplasms in Dogs. Cornell Vet., 30: 161â€”166, novo from histiocytes (15) or â€œprimitivepluripotent mesen 1940. chymeâ€• (9) in the dermis. Unfortunately, the morphogenesis 15. Moulton, J. E. Tumors of the Skin and Subcutis. In: Tumors in Domestic Animals. pp. 32â€”33. Berkeley and Los Angeles: Uni of CCH cannot be unequivocably defined until methods to versity ofCalifornia Press, 1961. experimentally transmit the tumor are developed. This and 16. Moulton, J. E. Tumors of the Vascular, Hemopoietic, and Lymph further attempts to detect an etiologic agent are worthy of oid Tissues. In: Tumors in Domestic Animals. p. 1 10. Berkeley and further study. Los Angeles: University of California Press, 1961. 17. Moulton, J. E. Tumors of the Urogenital System and Mammary ACKNOWLEDGMENTS Glands. In: Tumors in Domestic Animals. pp. 164â€”168.Berkeley and Los Angeles: University ofCalifornia Press, 1961. Assistance in the epizootiologic studies by Dr. Peter Schantz and Mr. 18. Mulligan, R. M. Neoplastic Diseases of Dogs. II. Mast Cell Sarcoma, Harold Hibbard is gratefully acknowledged, and the technical assistance Lymphosarcoma, Histiocytoma. Arch. Pathol., 46: 477â€”492@ of Miss Anna Wiener and Mr. S. Edward Brock is appreciated. We are 1948. indebted to the veterinary practitioners of Alameda and Contra Costa 19. Mulligan, R. M. Mast Cell Sarcoma, Lymphosarcoma, Histio Counties for their conscientious efforts in submitting neoplasms to the cytoma. In: Neoplasms of the Dog. pp. 93â€”95. Baltimore: The Wil Animal Neoplasm Registry. hams & Wilkins Co., 1949. 20. Orkin, M. and Schwartzman, R. M. A Comparative Study of Canine and Human Dermatology. II. Cutaneous Tumorsâ€”Introduction and REFERENCES Discussion of Transmissible Reticulum-Cell Tumor. A. M. A. Arch. Dermatol., 81: 347â€”358, 1960. 1. Bertalanffy, F. D. Acridine Orange Fluorescence Microscope Pro 21. Ottosen, H. E. Studies on Sarcomata of the Skin in Dogs. Nord. cedure.J. Am. Coil. Med. Tech., 1: 4â€”8, 1962. Veterinarmed., 1: 7â€”30, 1949. 2. Bloom, F. Spontaneous Solitary and Multiple Mast Cell Tumors. 22. Pearse, A. G. E. Appendix 11. Secondary Fluorescence Methods. (Mastocytoma) in Dogs. Arch. Pathol., 33: 661â€”676, 1942. In: Histochemistry, Theoretical and Applied. Ed. 2, p. 847. Bos 3. Dorn, C. R., Taylor, D. 0. N., Frye, F. L., and Hibbard, H. H. ton: Little, Brown and Company, 1961. Survey of Animal Neoplasms in Alameda and Contra Costa 23. Porter, K. R. Mesenchyma and Connective Tissue. In: R. 0. Greep, Counties, California. I. Methodology and Description of Cases. J. (ed.), Histology, Ed. 2, pp. 118â€”119.NewYork: McGraw-Hill Book Nail. Cancer Inst., 40: 295â€”305,1968. Company, 1966. 4. Dorn, C. R., Taylor, D. 0. N., Schneider, R., Hibbard, H. H. and 24. Richter, M. N. Spleen, Lymph Nodes, and Reticuloendothelial Klauber, M. R. Survey of Animal Neoplasms in Alameda and System. In: W. A. D. Anderson (ed.), Pathology. Ed. 3, Vol. 2, pp. Contra Costa Counties, California. II. Cancer Morbidity in Dogs 1034â€”1035. St. Louis: C. V. Mosby Co., 1966. and Cats from Alameda County. J. NaiL Cancer Inst., 40: 25. Rose, G. G. A Separable and Multipurpose Tissue Chamber. Texas 307â€”318, 1968. Rept. Biol. Med., 12: 1074â€”1083, 1954. 5. Dorn, C. R., Terbrusch, F. G. and Hibbard, H. H. Zoographic and 26. Smith, H. A. and Jones, T. C. Neoplasia. In: Veterinary Pathology. Demographic Analysis of Dog and Cat Ownership in Alameda Ed. 3, pp. 220â€”222.Philadelphia: Lea and Febiger, 1966.

88 CANCER RESEARCH VOL.29

Fig. 1. Dorsal view of a canine cutaneous histiocytoma in the skin of the lateral posterior thoracic region. There is early necrosis of the overlying epidermis. x 0.9. Fig. 2. Dorsal view of canine cutaneous histiocytoma at the commissure of the lips with ulceration of the overlying epidermis. x 1.5. Fig. 3. Lateral view of canine cutaneous histiocytoma. The epidermis is still intact. x 4. Fig. 4. Cut surface of a canine cutaneous histiocytoma which is a light shade of yellow. The neoplasm has lifted the epidermis off the dermis while separating but not elevating the hair shafts. x 4. Fig. 5. The canine cutaneous histiocytoma has expanded in the dermis widely dispersing the skin adnexia. It extends into the subcutis and entraps fat globules. There is no capsule but the deep margin prescribes a well-defined arc. Masson's trichome stain. x 6. Fig. 6. Histiocytic cells that are separated by interstitial spaces and appear individually discrete near the intact epidermis on the surface of a canine cutaneous histiocytoma. Hematoxylin and eosin, X 660. Fig. 7. Histiocytic cells separated by hemorrhage near the surface of an ulcerated canine cutaneous histiocytoma. Purulent exudate is present in the upper part of the photograph. Hematoxylin and eosin, x 425. Fig. 8. Impression smear of a canine cutaneous histiocytoma. The cytoplasm is vacuolated and/or granular. Nuclei are pleomorphic and have finely particulate, evenly dispersed chromatin. Multiple nucleoli are evident. The small dark-staining cells are lymphocytes. Geimsa, x 1000. Fig. 9. Histiocytic cells in the third tissue culture passage after 27 days incubation. The cytoplasm is vacuolated and the nuclei have finely particulate chromatin and multiple prominent nucleoli. Geimsa, x 660. Fig. 10. Histiocytic cells of a canine cutaneous histiocytoma that have abundant granular cytoplasm and indistinct cytoplasmic membranes. The nuclei are pleomorphic with rather scant nuclear chromatin which is sometimes peripherally marginated. Nucleoli are prominent and frequently multiple. Three mitotic figures are present. Hematoxylin and eosin, x 660. Fig. 1 1. Small numbers of dark-staining collagen fibers are widely separated by histiocytic cells in this section of a canine cutaneous histio cytoma. Masson's trichome stain, X 290. Fig. 12. Reticulum fibers in a section of a canine cutaneous histiocytoma. The fibers encompass large groups of histiocytic cells. Gordon and Sweet's reticulum stain, x 250. Fig. 13. Explant of a canine cutaneous histiocytoma in the lateral ventricle of a 7-day-old puppy inoculated during the last week of fetal life. Degenerating histiocytic cells are still evident among the collagen fibers of the explant, which may be recognized by the presence of 3 hair shafts. Hematoxylin and eosin, x 100.

JANUARY 1969 89

Dee a N. Taylor, @.RichardDorn, and Osman H. Luis

I-

@ ___@ @[email protected] @@______

;I @ 111111II IIIII III 0CM 4

90 CANCER RESEARCH VOL.29

-@. 4 â€˜I .@-â€˜..

Â®

JANUARY 1969 91

Dee a N. Taylor, C RichardDorn, and Osman H Luis

@@ .@Iâ€¢â€¢â€¢ -

@ ..-..--.,- â€¢@â€˜.. 4_â€¢d@' @:,. .@ @@@ @:@% @:.@ â€˜ - .: @. . -. @ â€˜ @s@-p. . iâ€•: â€˜-â€˜.@â€¢@...... - .. @ .- s@2f.@f@ (...

@ d ;â€˜:!@â€˜@ â€˜@::z @;@_; :; â€˜

@ râ€”@@@â€¢.::..@. ipt .: . â€¢. . _â€˜;..â€˜.@ @ .@:i:@di@.:â€˜,@-,.. T .. . . - - @@@@@ : ?t.:@:@t;....:Th.. â€˜. â€˜@ _..;â€˜@.I..): .-: @â€¢ . . @ - (;@â€”@; .- â€¢ : . ,@ - - .. @ - .. â€˜4:;'. . - .. - . â€¢ - . . . . . -. @ .$ ., . â€”...,. .. . - . *-...... -- - ,.. .

@@@ .4.. @.j..4 1

92 CANCER RESEARCH VOL.29

Dee O. N. Taylor, C. Richard Dorn and Osman H. Luis

Cancer Res 1969;29:83-92.

Updated version Access the most recent version of this article at: http://cancerres.aacrjournals.org/content/29/1/83

E-mail alerts Sign up to receive free email-alerts related to this article or journal.

Reprints and To order reprints of this article or to subscribe to the journal, contact the AACR Publications Subscriptions Department at [email protected].

Permissions To request permission to re-use all or part of this article, use this link http://cancerres.aacrjournals.org/content/29/1/83. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC) Rightslink site.