Adenosarcoma of the uterus with extensive smooth muscle differentiation: ultrastructural study and review of the literature.

Four cases of Mullerian adenosarcoma were studied by light and electron microscopy and immunohistochemistry. All 4 cases showed the histologic characteristics of adenosarcoma with benign endometrial glands and a malignant stroma. Ultrastructurally, the epithelial component in all cases had the appearance of proliferative endometrial glands, and the malignant mesenchymal cells showed features of endometrial stroma. A distinct basal lamina separating glands from stroma was present. In addition, 2 of the cases showed extensive smooth muscle differentiation which was associated with sarcomatous overgrowth. The smooth muscle features were confirmed by immunohistochemistry. Multiple theories of the histogenesis of this tumor are discussed.