OBJECTIVETo investigate neuroendocrine differentiation and Wilms' tumor protein-1 (WT-1) expression in breast mucinous carcinoma and their clinicopathological significance.

METHODSThe clinicopathological data of 65 patients with breast mucinous carcinoma, including 31 cases of mixed mucinous carcinoma, 23 cases of hypocellular pure mucinous carcinoma and 11 cases of hypercellular pure mucinous carcinoma, admitted in Taizhou Hospital from January 2010 to June 2015 were retrospectively reviewed. The expression of neuroendocrine markers and WT-1 was detected by immunohistochemistry staining in all cases.

RESULTSThe mixed mucinous carcinomas and hypercelluar pure mucinous carcinomas had higher incidence of axillary lymph node metastasis and human epidermal recepter 2 (HER-2) positive than hypocellular pure mucinous carcinoma (all (P<0.01). However, the difference was not significant between mixed mucinous carcinomas and hypercellular pure mucinous carcinomas (all P>0.05). The expression of neuroendocrine marker was stronger in hypercellular mucinous carcinoma than that in mixed mucinous carcinoma and hypocellular mucinous carcinoma (all (P<0.05), but the difference was not statistically significant between mixed mucinous carcinoma and hypocellular pure mucinous carcinoma (P>0.05). The expression of WT-1 was weaker in mixed mucinous carcinoma than that in hypercellular and hypocellular pure mucinous carcinoma(all (P<0.05), but the difference was not statistically significant between hypercellular and hypocellular pure mucinous carcinoma (P>0.05). The mucinous carcinomas with lymph node metastasis had lower expression of neuroendocrine markers than those without lymph node metastasis ((P<0.01). The expression of WT-1 in breast mucinous carcinoma with lymph node metastasis trended lower than that in those without lymph node metastasis, but the difference was not statistically significant (P>0.05).

CONCLUSIONHypercellular pure mucinous breast carcinoma has higher rates of lymph node metastasis and HER-2 amplification than hypocellular pure mucinous carcinoma, the sub-classification of breast pure mucinous carcinoma should be considered. Neuroendocrine differentiation and WT-1 expression may be helpful in distinguishing the subtypes of breast mucinous carcinoma. Breast mucinous carcinoma with neuroendocrine differentiation trends to have less lymph node metastasis.