OBJECTIVETo describe the morphologic features and immunohistochemistry of spindle cell carcinoma of breast with neuroendocrine differentiation.

METHODSRetrospective review of 2500 cases of breast carcinoma showed 5 cases (0.2%) with a predominance (> 80%) of spindle cell component. Amongst the 5 cases studied, 2 represented intraductal spindle cell carcinoma and 3 represented invasive spindle cell carcinoma. The paraffin sections were stained with hematoxylin and eosin, alcian blue, periodic acid-Schiff and reticulin stain. Immunohistochemical studies for AE1/AE3, CEA, EMA, CK7, 34betaE12, NSE, synaptophysin, chromogranin A, Leu-7, vimentin, S-100, SMA, calponin, estrogen receptor, progesterone receptor, c-erbB2, E-cadherin, Ki-67 and p53 were also carried out. Follow-up information was available in 4 of the 5 cases.

RESULTSThe mean age of the patients was 68 years. Histologically, all tumors were predominantly composed of elongated spindle cells. Three of these cases also contained tumor cells with vacuolated cytoplasm, alcian blue-positive tumor cells were observed in 4 cases. Immunohistochemically, the spindle tumor cells in all cases expressed AE1/AE3, CEA, EMA, E-cadherin and synaptophysin. CK7 was positive in 4 cases, NSE in 3 cases, chromogranin A and Leu-7 in 2 cases. Estrogen receptor was expressed in 4 cases and progesterone receptor in 2 cases. Overexpression of c-erbB2 oncoprotein was detected in only 1 case. Vimentin was focally positive in 1 case. Two cases of intraductal spindle cell carcinoma and 1 of the 3 cases of invasive spindle cell carcinoma were classified as neuroendocrine carcinoma of spindle cell type, while the remaining 2 cases of invasive spindle cell carcinoma were considered as metaplastic carcinoma with neuroendocrine differentiation. Amongst the 4 patients with follow-up information available, 3 were still alive 24 to 58 months after the initial diagnosis. One patient died within 27 months of diagnosis.

CONCLUSIONSThe presence of spindle tumor cells and sometimes intracytoplasmic mucin are useful morphologic clues in diagnosing spindle cell carcinoma of the breast with neuroendocrine differentiation. Intraductal neuroendocrine spindle cell carcinoma needs to be distinguished from usual ductal hyperplasia and intraductal papilloma. On the other hand, invasive spindle cell carcinoma with neuroendocrine differentiation needs to be distinguished from spindle cell myoepithelioma, malignant melanoma and sometimes soft tissue neoplasm.