SMALL-CELL (OAT-CELL) CARCINOMA OF THE BREAST

A case of small cell (oat cell) carcinoma, which represents both the m ost distinctive and the least common type of breast carcinoma with neu roendocrine differentiation and usually shows the most aggressive beha vior, is described. Radical mastectomy was performed on a 56-year-old female for a 10 cm tumor located in the outer part of the right breast with cutaneous ulceration Microscopically, the tumor predominantly co nsisted of a diffuse proliferation of small, round to ovoid cells with hyperchromatic nuclei and ill-defined, scant cytoplasm that was remin iscent of oat cell carcinoma of the lung. There were foci of invasive ductal carcinoma and ductal carcinoma in situ. Small cell carcinoma ar eas constituted approximately 90% of the neoplasm. The patient had axi llary lymph node metastasis. The small tumor cells were argyrophilic a nd positive for CAM5.2, carcinoembryonic antigen, neuron-specific enol ase, Leu-7, chromogranin A and synaptophysin. Flow cytometric analysis showed an aneuploid DNA content. The patient was alive and well witho ut: disease 4 years after surgery. Small cell carcinomas of the breast may exhibit a spectrum of malignancy that is comparable to similar tu mors at better known primary sites.