Table 1.

Summary table of primary neuroendocrine carcinoma of the breast.

Etiology	Uncertain
Incidence	<0.1% of all mammary carcinomas
Gender ratio	Female predominance
Age predilection	Sixth decade of life
Risk factors	Not known
Treatment	Surgical resection and chemotherapy (optimal adjuvant therapy is still unknown)
Prognosis	Worse than invasive mammary carcinoma Wang et al. 2014 SEER study showed median survival duration of NEC cases was much shorter than that of IMC-NOS cases (26 months in NEC; 34 months in IMC-NOS)
Imaging findings	Nonspecific and cannot be differentiated from in situ breast carcinoma without biopsy. Mammogram: high-density spiculated mass, ultrasound: hypoechoic or heterogeneous irregular mass with normal sound transmission, MRI: heterogeneous low T1, high T2, enhancing mass with rapid initial enhancement and delayed washout

IMC-NOS, invasive mammary carcinoma not otherwise specified case; MRI, magnetic resonance imaging.