Abstract
BACKGROUND: Primary large-cell neuroendocrine carcinoma of the breast (LCNEC-breast) in pre-menopausal women is extremely rare. CASE REPORT: A 34-year-old woman presented with a mass in the left breast that was diagnosed as neuroendocrine carcinoma by needle biopsy. Computed tomography revealed no lymph node swelling or distant organ metastasis. Left mastectomy and sentinel lymph node biopsy were performed and metastasis to the axial lymph node was detected. Left axillary lymph node dissection was performed and histopathological and immunohistochemical examination revealed that the tumor was an LCNEC-breast, which was 6.0 cm in size and positive for the neuroendocrine markers (neuron-specific enolase, chromogranin A, and synaptophysin). The tumor cells were hormone-receptor positive and HER2 negative. The patient refused any adjuvant hormonal therapy, chemotherapy or radiotherapy. She has been followed up for 4 years without medication, and no recurrence has been noted. CONCLUSION: We present a case of LCNEC-breast in a 34-year-old woman. Our case represents the youngest woman with LCNEC-breast reported in the English literature.