Differential Diagnosis between Uterine Carcinosarcoma versus Carcinoma with Sarcomatous Metaplasia: An Immunohistochemical and Ultrastructural Case Study

Uterine carcinosarcomas are biphasic neoplasms with carcinomatous and sarcomatous elements. However, several elements suggest that carcinosarcomas may be more closely related to carcinoma of the endometrium and that they arise from an unique stem cell. Recently, the authors observed an uterine tumor that at histologic examination showed an apparently double population of cells: malignant epithelial element admixed with mesenchymal spindle-shaped cells. The immunohistochemical stainings instead showed cytokeratin positivity and negativity for stromal markers. Electron microscopy showed the neoplastic tissue to be made of a single population of poorly differentiated epithelial cells, thus confirming the immunohistochemical findings and leading to the diagnosis of uterine metaplastic carcinoma.