Small cell carcinoma of the breast ings, a large irregular mass was incidentally detected in took a biopsy of the breast mass to confirm the pathology. the left breast with overlying skin thickening and nipple Microscopic finding showed infiltrating nests of small retraction. The breast mass was evaluated by mammog- cells in the fibrotic stroma, the tumor cells of which had raphy and sonography. On mammography, an ill-defined small hyperchromatic nuclei and scanty cytoplasms (Fig. hyperdense mass occupied the left subareolar area which 2A). Immunohistochemical stain showed strong positivity was adherent to the areola (Fig. 1B). Nipple retraction, dif- of the tumor cells for neuron-specific enolase, suggestive fuse skin thickening, and multiple enlarged lymph nodes of small cell neuroendocrine carcinoma (Fig. 2B). in the left axilla were noted with shrinkage of the volume of the left breast. An irregular hypoechoic mass with in- vasion to the nipple was demonstrated on sonography (Fig. 1C). Abdominal and pelvic CT and positron emission DISCUSSION tomography-CT were obtained to check the other organs Primary neuroendocrine carcinomas of the breast ex- of the body, and showed no evidence of abdominal or pel- hibit morphologic features similar to neuroendocrine tu- vic lesions. The final diagnosis of the imaging studies was mors of the gastrointestinal tract and lungs. Primary neu- a primary breast tumor with pulmonary metastasis. We roendocrine carcinomas express neuroendocrine markers Fig. 1. (A) Sonography showed small irregular hypoechoic lesion with angular margin and spiculations (arrows). (B) Mammography showed ill-defined hyperdense mass in left subareolar area which was adherent to areola. Nipple retraction, diffuse skin thickening, and multiple enlarged lymph nodes in left axilla were noted with shrinkage of volume of left breast. (C) Sonography showed irregular hypoechoic mass with invasion to nipple (arrows). Fig. 2. (A) Microscopic finding showed infiltrating nests of small cells in fibrotic stroma. Tumor cells had small hyperchromatic nuclei and scanty cytoplasms (H&E, ×200). (B) Immunohistochemical stain showed strong positivity of tumor cells for neuron-specific enolase (×400). thesurgery.or.kr 117