[Histopathologic study of uterine adenomatoid tumor with special reference to histogenesis]

Twenty cases (13 from Jichi Medical School Hospital and 7 from other hospitals) of uterine adenomatoid tumor (ADT) were examined histochemically, immunohistochemically and ultrastructurally, to determine the histogenesis. For the control study, cases of malignant mesothelioma, reactive mesothelial hyperplasia, ADT of male genital organs and appendix testis were also examined. The results were summarized as follows: The age of the patients at hysterectomy ranged from 37 to 62 years with a mean of 44.6 years. Thirteen uteri containing ADT were found among 1250 hysterectomized specimens (the frequency, 1.04%) over the past 10 years at Jichi Medical School Hospital. The tumors were incidentally detected within the uteri which were removed for other genital conditions except for two cases with clinical symptom from ADT. Eighteen cases of ADT were small, non-encapsulated nodular lesions resembling adenomyosis uteri, and 12 cases were situated at the left cornual region of the uterine subserosa. The tumor cells showed a vivid production of hyaluronic acid and a positive staining reaction for intracytoplasmic keratin, but negative for factor VIII-related antigen in all cases. Ultrastructurally, the tumor cells were characterized by numerous, well-developed microvilli, abundant tonofilaments and tonofibrils frequently associated with desmosomes. The present findings were identical to those for malignant mesothelioma, reactive mesothelial hyperplasia and ADT of male genital organs, but not identical to those for appendix testis. In the light of the location, histopathological features and proliferative behavior of uterine ADT, it was considered to be a choristoma rather than a true neoplasm, namely, a malformational non-neoplastic lesion composed of heterotopic mesothelial cells.