Breast Metastasis From Cervical Small Cell Neuroendocrine Carcinoma Mimicking Primary Breast Cancer.

We describe a case of breast metastasis originating from a small-cell neuroendocrine carcinoma (SCNEC) of the uterine cervix, an uncommon presentation that can be difficult to distinguish from a primary breast malignancy. We report a 29-year-old woman treated three years earlier for FIGO stage IB2 cervical SCNEC with chemotherapy, surgery, and radiotherapy, who presented with a 1.5-cm mass in the left breast. Imaging suggested a primary breast malignancy, but her oncologic history raised concern for metastasis. Core-needle biopsy showed a high-grade small-cell neoplasm expressing synaptophysin, chromogranin A, and CD56, with a high Ki-67 index (>80%); breast-lineage markers, including GATA3 and mammaglobin, were negative. Whole-body fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) showed an isolated hypermetabolic breast lesion without other disease. Nipple-sparing mastectomy with immediate reconstruction was performed, followed by platinum-etoposide chemotherapy; at 18 months, there was no evidence of recurrence. Breast metastasis from cervical SCNEC can mimic primary breast cancer; diagnosis relies on integrating clinical history, imaging, and immunohistochemistry. Selected patients with isolated disease may benefit from individualised multimodal therapy.