Objective  This study aimed to approach the clinicopathological characteristics of primary neuroendocrine breast carcinoma(pNEBC) and to identify related factors of lymph node metastasis. Methods We retrospectively collected the clinical data of patients in Department of Breast Surgery, Peking Union

  Medical  College Hospital from November 2004 to October 2016.The patients who were diagnosed as pNEBC were selected as the study group (pNEBC group). Meanwhile, the patients who were operated at the same time and diagnosed as invasive carcinoma of no special type(NST) were selected as the control group (NST group). The clinico-pathological characteristics and lymph node metastasis-related factors of the two groups were compared.

  Results  Following the inclusion and exclusion criteria, a tolal of 50 patients diagnosed as pNEBC and 200 patients diagnosed as NST were included in this study.There was no significant difference in age, tumor diameter, histological grade, number of lymph nodes dissected, and TNM stage between the two groups (all P > 0.05). The baseline level of the two groups was similar. Fifteen pNEBC patients(30.0%, 15/50) had lymph node metastasis. The expressions of estrogen receptor(ER), progesterone receptor(PR), and human epidermal growth factor receptor-2(Her-2) status were 96.0%, 84.0%, and 10.4%, respectively. The expressions of chromogranin A(CgA) and synaptophysin(Syn) were 58.0% and 97.9%, respectively. In the analysis of related factors affecting the lymph node metastasis, there was no significant difference in the histological grade, immunohistochemical index, and molecular typing between the two groups(all P > 0.05). There existed significant differences in the T stage in the control group (P=0.006), while no difference found in the study group (P=0.872).

  Conclusions  pNECB is often positive for hormone receptors, but almost negative for Her-2. The positive expression rate of Syn is higher than that of CgA. Although interfering factors on the prognosis of pNEBC are still controversial, its biological behavior needs further study and more attention should be paid to joint detection of the above immunohistochemical indicators and lymph node status.