Neuroendocrine differentiated carcinomas of the breast: a distinct entity

Some primary carcinomas of the breast have been classified as neuroendocrine. In this paper we report on 12 cases of neuroendocrine carcinoma of the breast displaying common and uncommon histological features. MATERIALS AND METHODS: All patients were aged from 43 to 79 (median 66.5) years. The tumors were unilateral and ranged from 0.8 to 7 cm (median 2.35 cm) in diameter. Four tumors were classified as solid cohesive, two as solid papillary, one as Merkel cell-like, two as cellular mucinous, two as cellular mucinous with micropapillary features and one as cellular mucinous with prominent signet ring cells. The tissues were fixed in formalin and routinely processed. All materials were stained with PAS, Alcian blue and also hematoxylin and eosin. Immunohistochemical examination was carried out by the avidin-biotin method using the following antibodies: estrogen receptor protein, progesterone receptor protein, p53, cerbB-2, Ki67, neuron-specific enolase, chromogranin, and synaptophysin. RESULTS: In all cases the tumor cells were stained positively with NSE. Synaptophysin and chromogranin positivity was detected in 11 and five cases, respectively. The prominent histological features were: extensive intraductal growth, pseudorosettes and palisades, low-grade cytologic atypia, plasmacytoid appearance of the tumor cells, and intracellular and extracellular mucin. CONCLUSION: Neuroendocrine-differentiated carcinoma of the breast is a rare and distinct category with different histological subtypes.