Dachshund 1 is Differentially Expressed Between Male and Female Breast Cancer: A Matched Case-Control Study of Clinical Characteristics and Prognosis.

INTRODUCTION: Male breast cancer (MBC) is rare and little is known about its biological behavior. In this study we described clinical characteristics and prognosis of MBC and evaluated roles of different factors between MBC and female breast cancer (FBC).

PATIENTS AND METHODS: We retrospectively reviewed 42 MBC patients matched with 84 consecutive FBC patients with similar year, age, tumor, node, metastases (TNM) stage, and estrogen receptor (ER) expression from 2003 to 2016. Their clinical characteristics, treatments, and prognosis were analyzed, and immunohistochemistry for androgen receptor (AR), dachshund 1 (DACH1), sine oculis 1 (SIX1), eyes absent 1, B-cell lymphoma-2, and p53 were performed on paraffin sections.

RESULTS: MBC constituted 0.56% (42 of 7561) of consecutive breast cancer and had a median age of 55 years. The 14 paraffin samples from men and 28 from women expressed all the assessed proteins, and DACH1 was significantly higher in women (P = .043). Body mass index (P = .023) and DACH1 (P = .034) were correlated with MBC prognosis, whereas the expression of AR (P = .049), SIX1 (P = .048), surgery (P < .001), and chemotherapy (P = .001) were important for FBC in addition to already known factors: tumor size and location, TNM stage (lymph nodes and organ metastasis), radiotherapy, and ER and human epidermalgrowth factor receptor-2 (HER2) expression. No distinct difference in recurrence was observed between MBC and FBC (P = .667).

CONCLUSION: In this study we found that DACH1 was expressed less in MBC and HER2 was expressed more in FBC. They were respectively correlated with MBC and FBC prognosis. Although no significant differences were observed between MBC and FBC prognosis, DACH1, SIX1, and AR expression requires greater attention to develop treatment strategies for MBC and FBC.