Morphologic and Biologic Characteristics of the Canine Cutaneous Histiocytoma'
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[CANCER RESEARCH 29, 83—92,January 1969] Morphologic and Biologic Characteristics of the Canine Cutaneous Histiocytoma' 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 “extragenitalvenereal tu Contra Costa Counties, California, during 3 years were col mors― 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 “clearlydistinguishable 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, and—despite claims to the contrary—is morpholog than all other breeds, and purebred dogs in general had a high ically distinct from transmissible venereal tumor of the dog.― 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 4°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 ‘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 Downloaded from cancerres.aacrjournals.org on October 1, 2021. © 1969 American Association for Cancer Research. Dee 0. N. Taylor, C. Richard Dorn, and Osman H. Luis 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 36°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.