Neuroendocrine carcinoma of the breast (NECB) is a rare and aggressive malignancy, accounting for <1% of all breast cancer cases. This report describes the case of a 60-year-old postmenopausal woman who presented with a painless mass in her left breast. Clinical examination and imaging revealed an irregular lesion classified as Breast Imaging Reporting and Data System V. The patient underwent breast-conserving surgery along with axillary lymph node dissection. Histopathological examination and immunohistochemistry confirmed the diagnosis of invasive neuroendocrine carcinoma (pT2N1a). The tumor cells were positive for estrogen receptor, progesterone receptor, synaptophysin, and GATA binding protein 3 but negative for human epidermal growth factor receptor 2 (HER2/neu). Adjuvant treatment included chemotherapy, radiotherapy, and hormonal therapy. This case highlights the diagnostic challenges and management strategies associated with this rare condition, emphasizing the critical role of histopathological and immunohistochemical evaluations in achieving an accurate diagnosis. Due to the rarity of NECB, treatment protocols are typically extrapolated from those used for invasive ductal carcinoma, underscoring the need for further research to establish optimal management strategies.