ANGIOSARCOMA-LIKE NEOPLASMS OF EPITHELIAL ORGANS - TRUE ENDOTHELIAL TUMORS OR VARIANTS OF CARCINOMA

Past experience has shown the existence of tumors in various viscera t hat assume growth patterns that are usually associated with angiosarco mas of skin and soft tissue. The lineage of differentiation pursued by the former of these proliferations has been the subject of controvers y, with some investigators concluding that ''angiosarcomatoid'' neopla sms of solid organs were, in actuality, variants of high-grade carcino mas. The latter statement does appear to have partial validity, inasmu ch as immunohistologic, ultrastructural, and clinical data on ''pseudo vascular carcinomas'' do support their basic identity with high-grade epithelial malignancies of the breasts, skin, and lungs. Those lesions show uniform reactivity for keratin and epithelial membrane antigen, but they fail to express von Willebrand factor, CD31, or CD34, which a re regarded as endothelial determinants. On the other hand, however, a ngiomatoid neoplasms of the thyroid gland are more complex; some repre sent indisputable carcinomas, others manifest seemingly ''pure'' mesen chymal phenotypes, and still others display a mixture of epithelial an d endothelial phenotypes at ultrastructural and protein-chemical level s of specialized investigation. At present, it must be acknowledged th at the distinction between angiomatoid thyroid carcinomas and ''true'' thyroid angiosarcomas is an academic one, because the prognoses and t reatments for these lesions are essentially identical. Copyright (C) 1 995 by W.B. Saunders Company