J Clin Pathol: first published as 10.1136/jcp.35.12.1380 on 1 December 1982. Downloaded from

J Clin Pathol 1982;35:1380-1383

Fatty tumours of the uterus

DERRICK J POUNDER From the Division of Tissue Pathology, Institute ofMedical and Veterinary Science, Adelaide, South Australia

SUMMARY Uterine fatty tumours (UFI) are uncommon and have received little attention in the English literature. They have aroused interest as a consequence of occasional diagnostic confusion with sarcomas and the continuing unresolved dispute as to their histogenesis. Three cases of UFT are described and the pathological features of note discussed. The viewpoint that these tumours are hamartomas/choristomas is rejected. UFT most probably represent tumour metaplasia within a leiomyoma. There is no uniform accepted nomenclature for such tumours and it is suggested that they be designated "uterine fatty tumours" and subdivided into "lipoma" and "mixed lipoma/ leiomyoma" (synonym lipoleiomyoma).

Fatty tumours primary to the uterus are uncommon' normal Fallopian tubes. There was a very large intra- and are almost invariably benign.2 Occasionally the mural uterine tumour mass which measured 200 mm clinical presentation3 or macroscopic appearance2 in greatest diameter and weighed 2140g. The tumour, may mimic a sarcoma and create diagnostic con- which distorted the uterine cavity into an enlarged fusion. There is no consensus as to the histogenesis or slit, was rounded and well circumscribed but not nomenclature of uterine fatty tumours (UFT).45 encapsulated. On cut surface the greater part of the copyright. Three cases of UFT are presented and discussion tumour appeared yellow, lobulated and fatty. Within centres on these areas of interest and contention. the tumour mass and abutting upon one margin was a hard, grey calcified wedge measuring 120 x 80 x 75 Material and methods mm. Two typical spherical, circumscribed leio- myomas, each approximateiy 15 mm in diameter, All uterine fatty tumours (UFT) accessioned on the were also identified within the myometrium. files of the Institute of Medical and Veterinary Microscopically, the fatty tumour comprised adult- Science6 over a three-year period, January 1979 to type adipose tissue divided into lobules by thin http://jcp.bmj.com/ January 1982, were retrieved. Amongst the connective tissue septae. There was no true tumour approximately 54 000 surgical accessions during this capsule but adjacent myometrium was compressed period there were three cases of UFT. Nine, two and around the tumour to provide a false capsule. one paraffin blocks of tumour tissue were available Irregularly dispersed amongst the adipocytes were from these three cases for review. Haematoxylin and single and small clusters of smooth muscle cells. In eosin-stained and, where appropriate, Masson some areas of the tumour the smooth muscle trichrome-stained sections from each paraffin block component could be identified only after careful on September 30, 2021 by guest. Protected were studied. searching whilst in other areas groups of smooth muscle cells were readily apparent. Smooth muscle Results cells were present deep within the tumour as well as at its periphery. Nowhere did the smooth muscle A summary of the relevant clinical history, clinical component form the wide interlacing and whorled diagnosis and final diagnosis for the three cases bands typically seen in a leiomyoma. The hard studied is set out in the Table. The pathological calcified wedge identified macroscopically comprised diagnosis of a UFT was confirmed in each ofthe three degenerate adipose tissue with an extensively hyalin- cases and only the pathological findings relevant to ised connective tissue stroma and heavy calcification this diagnosis will be described in detail. of adipocytes. Similar smaller foci of hyaline sclerosis and dystrophic calcification of adipocytes were dis- CASE 1 (FIGS. 1 AND 2) posed irregularly throughout the tumour. The two The resected specimen comprised a uterus with two small leiomyomas identified macroscopically showed some stromal hyalinisation but did not contain an Accepted for publication 2 June 1982 adipose tissue component. 1380 J Clin Pathol: first published as 10.1136/jcp.35.12.1380 on 1 December 1982. Downloaded from

Fatty tumours of the uterus 1381 Clinical details ofthree cases ofuterinefatty tumour Case Age (yr) Clinical history Clinical diagnosis Final diagnosis 1 83 Five years increasing weight and ? Ovarian cyst Uterine mixed lipoma/leiomyoma, abdominal girth; initially refused ? Uterine leiomyoma cervical dysplasia (moderate), uterine surgery; oedema of right leg for one leiomyomas (2) week 2 80 Long-standing uterine prolapse Uterine prolapse Uterine prolapse, cervical keratinisation, uterine leiomyoma, uterine mixed lipoma/leiomyoma 3 73 Post-menopausal bleeding, large Ovarian tumour Mucinous cystadenocarcinoma (right pelvic mass; curetting-hyperplastic ovary), hyperplastic endometrial polyps polyp, uterine mixed lipoma/leiomyoma

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'... I /~~~~~~~~~~~. 1% ,i I~ http://jcp.bmj.com/ Fig. 2 Clusters ofsmooth muscle cells are scattered amongst Fig. 1 An intra-mural mixed lipoma/eiomyoma (case 1) the adipocytes (case 1). Masson's trichrome x 60 The atrophic endometrium is seen at the top ofthe photomicrograph. Note the lack ofbroad smooth muscle fascicles within the tumour which is predominantly fatty. Masson's trichrome x 20 smaller nodule in the lower uterine segment was a leiomyoma without any adipose tissue component. on September 30, 2021 by guest. Protected CASE 2 (FIG. 3) CASE 3 (FIG. 4) The simple hysterectomy specimen comprised a The surgical specimen was a total hysterectomy with uterus with parous cervix. A spherical, yellow and bilateral salpingo-oophorectomy. At the uterine white, circumscribed nodule 25 mm in diameter was fundus was a subserosal, circumscribed, yellow and sited intramurally at the fundus. A second cir- white nodule 20 mm in diameter. Microscopically, cumscribed intramural nodule 8 mm in diameter was this fundal nodule resembled the UFT in case 2 present in the lower uterine segment. above. The smooth muscle component was more Microscopically the larger nodule was circum- prominent and approximately 10% of the tumour was scribed but not encapsulated and comprised an occupied by broad whorling bands of smooth muscle intimate admixture of adult-type adipose tissue, in a pattern typically seen in uterine leiomyomas. The smooth muscle fascicles and a dense hyalinised smooth muscle component was primarily localised to stroma. The adipose tissue component was the periphery of the tumour whilst centrally there was prominent and readily identified. The stromal extensive hyalinisation. Adipocytes were sparsely hyalinisation and the quantity of blood vessels scattered amongst the bands of smooth muscle but resembled that seen in a typical leiomyoma. The were very prominent centrally. J Clin Pathol: first published as 10.1136/jcp.35.12.1380 on 1 December 1982. Downloaded from

1382 Pounder

JI 19. J 13utere UtvCtV it il &Vtyutina atr urt&tUn"&-#'*-IV `':0KA. T.' -W-wr_-II---:%- _. amongst adjacent smooth muscle fascicles (case 2) x 60 Fig. 4 A few adipocytes are present within an otherwise typical leiomyomatous area (case 3). An artefactual cleft formed between the tumour and its compression capsule is Discussion seen at the top ofthephotomicrograph x 60

Uterine fatty tumours (UFT) may be defined as 003% and 0 2%' of leiomyomas. Pure leiomyomas copyright. tumours composed entirely or in part of adult-type are frequently found in association with UF1T2 and adipose tissue. Smooth muscle and fibrous tissue are this was so in two cases. UFT may be multiple. 10 usually intermixed. As the present cases illustrate, Fatty areas within a UFT appear yellow or yellow- the relative proportion of these tissues varies widely grey and feel soft.4 As in case 1 the entire tumour may both within and between tumours. This range of appear distinctly fatty.3 Occasionally a discrete fatty histopathological appearances has caused a pro- focus may be present within an otherwise typical liferation of synonyms2 for UFT. The more common leiomyoma.5 Most commonly the adipose tissue is synonyms include lipoleiomyoma, myolipoma, lipo- scattered throughout the tumour (see cases 2 and 3). http://jcp.bmj.com/ fibroma, lipomyoma, fibromyolipoma, mixed A UFT which is soft with a homogeneous non-fibrillar lipoma, and lipomatosis of the stroma of a uterine cut surface may suggest a diagnosis of leiomyo- fibroid. There is no common numerical code alloca- sarcoma.2 The differential diagnosis lies between ted to UFT in the systematised nomenclature of a sarcoma, UFT and leiomyoma with ischaemic medicine of the College of American Pathologists.' degeneration or necrosis. At operation a frozen The average age of the three cases was 79 yr, in section should resolve the dilemma.'0 Malignant fatty

keeping with reports that more than 90% of UFT tumours primary to the uterus are exceptionally rare.2 on September 30, 2021 by guest. Protected occur in patients over the age of 40 yr.5 Only one Microscopically, all UFT contain adult-type fat patient was symptomatic as a consequence of the cells. Most tumours contain easily recognisable areas UFT. The spectrum of clinical presentation of UFT of smooth muscle either as broad interweaving effectively parallels that of uterine leiomyomas.'5 fascicles or scattered myocytes. The fibrous tissue Consequently the correct diagnosis is rarely made stroma may be delicate or dense and hyalinised, and preoperatively8 unless by x-ray or ultrasound.9 Rapid the vascular component is said occasionally to be growth of a UFT may suggest a clinical diagnosis of striking.4 Scattered mast cells and eosinophils may be sarcoma.3 found2 but were not observed in any of the present All three tumours were located in the uterine cases. These stromal components may also be seen in corpus which is the typical site. Occasionally UFT pure leiomyomas. The overall impression is of a arise in the cervix.5 Two tumours were intramural and histological spectrum ranging from pure lipoma the third was subserosal, a less common location.2 through mixed lipoma/leiomyoma to pure The two smaller tumours macroscopically resembled leiomyoma. leiomyomas except for their yellow colouration. UFT There are no clearly established histopathological are variously reported as representing between criteria for the distinction of a pure lipoma from a J Clin Pathol: first published as 10.1136/jcp.35.12.1380 on 1 December 1982. Downloaded from

Fatty tumours of the uterus 1383 mixed lipoma/leiomyoma of the type illustrated by extremely tenuous. case 1. The presence of occasional scattered smooth The adipose tissue within UFT more likely than not muscle cells is interpreted by some as representing represents fatty metaplasia within a leiomyoma.'9 inclusion of myometrium by an expanding lipoma.2 I Such "tumour metaplasia" is a well recognised concur with the viewpoint' that a diagnosis of pure phenomenon. 14 Metaplasia may also occur within the lipoma of the uterus should only be made when any stroma of a tumour-for example, osseous meta- smooth muscle cells present are confined to the plasia in a carcinoid of the lung. The sometimes florid periphery of the tumour. Only then can the myocytes overgrowth of adipose tissue within a UFT as in case 1 be accepted as having been incorporated by an suggests that it represents tumour cell metaplasia expanding lipoma. rather than stromal metaplasia. However, the The term mixed lipoma/leiomyoma is descriptive clarification of the precise histogenesis of UFT must and serves to emphasise the clinical and macroscopic await the complete elucidation of the histogenesis of similarity of these tumours to leiomyomas. These leiomyomas of the uterus.8 tumours might also be designated as lipoleiomyomas. Division of the mixed lipoma/leiomyoma group into References two subgroups,'2 namely circumscribed lipomatosis 'Willen R, Gad A, Willen H. Lipomatous lesions of the uterus. in a myoma and diffuse lipomatosis in a myoma Virchows Arch A PatholAnat Histol 1978;377:351-61. emphasises differences in the macroscopic 2 Jacobs DS, Cohen H, Johnson JS. Lipoleiomyomas of the uterus. Am J Clin Pathol 1965;44:45-51. appearance (vide supra) but seems unnecessarily 3Gupta RK, Hunter RE. Lipoma of the uterus: review of literature wieldy. Some4 have used the term "benign mixed with views of histogenesis. Obstet Gynecol 1964;24:255-7. mesodermal tumours" for these lesions. There does 4Demopoulos RI, Denarvaez F, Kaji V. Benign mixed mesodermal not appear to be a close relationship between UFT tumours of the uterus: a histogenetic study. Am J Clin Pathol 1973;60:377-83. and malignant mixed mesodermal tumours." 12 Brandfass RT, Everts-Suarez EA. Lipomatous tumours of the Theories on histogenesis lay emphasis upon uterus. A review of the world's literature with report of a case of explaining the presence of adipose tissue, an element true lipoma. Am J Obstet Gynecol 1955;70:359-67. not usually found in the uterine corpus.45 Most 'Allen PW, Angus BV. Computer-output microfilm in an anatomic copyright. pathology laboratory. Am J Clin Pathol 1978;69:537-43. recently a morphological and histogenetic analogy Cote RA. Systematised nomenclature ofmedicine. Illinois: College has been drawn between UFT and renal of American Pathologists, 1977. angiomyolipomas." '1' " It has been suggested that 8Honore LH. Uterine fibrolipoleiomyoma: report of a case with UFT are hamartomas or, more appropriately, discussion of histogenesis. Am J Obstet Gynecol 1978;132:635- 6. choristomas. '4 Renal angiomyolipomas are con- 9 Houser LM, Carrasco CH, Sheehan CR. Lipomatous tumour of sidered to be choristomas. 15 the uterus: radiographic and ultrasonic appearance. BrJ Radiol Quantitative comparisons between UFT and 1979;52:992-3. angiomyolipomas have revealed a similarity in the '° Chachutow D, Brill R, Passaic NJ. Lipomas of the uterus. Am J http://jcp.bmj.com/ Obstet Gynecol 1957;73:1358-61. proportions ofadipose and smooth muscle elements.4 "Norris HJ, Taylor HB. Mesenchymal tumours of the uterus. III A Abnormal vascular proliferations have also been clinical and pathological study of 31 carcinosarcomas. Cancer described in UFT.4 However, these comparisons 1966;19:1459-65. remain unconvincing because there are significant 2 Kempson RL, Bari W. Uterine sarcomas. Classification, diagnosis and prognosis. Hum Pathol 1970;1:331-49. qualitative differences between renal angio- 3 McKeithen WS, Shinner JJ, Michelsen J. Hamartoma of the myolipomas and UFT. The smooth muscle in uterus. Report of a case. Obstet Gynecol 1964;24:231-4. renal angiomyolipomas is often unusual in that the ' Walter JB, Israel MS. General pathology. 5th ed. Edinburgh: on September 30, 2021 by guest. Protected myocytes appear cytologically atypical.'6 Also renal Churchill Livingstone, 1979. "Bennington JL, Beckwith JB. Tumors of the Kidney, Renal Pelvis angiomyolipomas have an infiltrating margin. These and Ureter (Atlas of tunor pathology, 2nd series fascicle 12). features are not seen in UFT. To the best of my Washington: Armed Forces Institute of Pathology, 1975. knowledge histopathologically convincing extra- 6 Allen PW. Tumors and proliferations ofadipose tissue. A clinico- renal angiomyolipomas have only been described in pathological approach. New York: Masson, 1981. Ishak KU. Mesenchymal tumours ofthe liver. In: Okuda K, Peters the liver.'7 RL, eds. Hepatocellular carcinoma. New York: John Wiley and The viewpoint that renal angiomyolipomas are Sons, 1976:247-305. choristomas is strengthened by their association 18 Donegani G, Grattarola FR, Wildi E. Tuberous sclerosis: with choristomas/hamartomas in other organs.'8 Bournevllle disease. In: Vinken PJ, Bryun GW, eds. Handbook of clinical neurology. Amsterdam: North Holland Publishing By contrast UFT are associated with uterine Co, 1972:14:340-89. leiomyomas.2 Furthermore, the entire spectrum of "Gonzalez-Angulo A, Kaufman RH. Lipomatous tumor of the renal smooth muscle and fatty tumours are regarded Uterus. Report of a case. Obstet Gynecol 1962;19:494-8. as choristomas. '5 By contrast uterine leiomyomas are Requests for reprints to: Dr Derrick J Pounder, Division of generally regarded as true neoplasms. Thus the Tissue Pathology, Institute of Medical and Veterinary analogy between UFT and renal angiomyolipomas is Science, Frome Road, Adelaide S.A. 5000, Australia.