Amphicrine medullary carcinoma of the thyroid with luminal differentiation: report of an immunohistochemical and ultrastructural study.

A case of amphicrine medullary carcinoma of the thyroid is presented. The patient was an 18-year-old female with nonhereditary MEN IIb, submucosal neuromas in the oral cavity, and a thyroid tumor that metastasized to regional lymph nodes. Histologically the thyroid tumor was composed of polygonal cells arranged in a solid/trabecular pattern admixed with mucus-producing goblet cells and displaying focal cytoplasmic lumen formation. Immunohistochemical stains were positive for calcitonin, carcinoembryonic antigen, and chromogranin. Electron microscopy demonstrated C-cells containing neurosecretory granules as well as intestinal-type microlumina. The presence of goblet cells and intestinal-type microlumina in medullary carcinoma of the thyroid is reminiscent of amphicrine tumors of the gastrointestinal tract and supports the hypothesis that the parafollicular C-cells of the thyroid may be of endodermal derivation.

Epithelioid angiosarcoma of the breast. Clinicopathological, immunohistochemical, and ultrastructural study of a case.

A breast tumor with features of epithelioid angiosarcoma (EAS) occurring in a 26-year-old woman is described. The lesion on lumpectomy was initially diagnosed as infiltrating ductal carcinoma and treated accordingly by radical mastectomy. The surgical specimen disclosed a high-grade tumor characterized by solid groups and sheets of atypical polygonal epithelioid cells displaying cytoplasmic microlumina alternating with anastomosing vascular channels. The endothelial nature of the epithelioid cells was demonstrated by the presence of vascular endothelium-associated markers by immunohistochemical and ultrastructural studies. The clinical features of this rare, hitherto undescribed lesion are similar to those of conventional breast angiosarcoma. The recognition of this entity is crucial because it can be confused with neoplasms displaying epithelial cytomorphology such as ductal carcinoma, pseudoangiosarcomatous carcinoma, metaplastic carcinoma, and epithelioid hemangioendothelioma. EAS should be added to the list of conditions that may present as a discrete tumor mass of the breast in young women.