Male breast cancer: clinicopathological characterization of a National Danish cohort 1980–2009

BACKGROUND: To describe relevant pathological parameters of Danish male breast cancer patients (MBCP) diagnosed from 1980 to 2009, and to relate these data to treatment, overall survival (OS) and standardized mortality rate (SMR). MATERIALS AND METHODS: The MBCP cohort was defined from national Danish registers. A total of 643 MBCP were identified with tissue available in 457. Among these, 384 were primary operable. Where tissue blocks were available, tumor type, grade, estrogen receptor (ER), progesteron receptor (PgR) and androgen-receptor (AR) status as well as HER 2 and Ki67 were performed. OS was quantified by Kaplan–Meier estimates and SMR was calculated based on mortality rate among patients relative to the mortality rate in the general population. RESULTS: Male breast cancer was more often of ductal type, grade II and a very high proportion were ER and AR positive and HER2 negative. Intrinsic subtypes based on immunohistochemical evaluation showed luminal subtype. Ki67 ratio increased over period of study. OS declined by increased age, bigger tumor size, positive lymph node status, higher grade and Luminal B subtype. Hazard ratio and relative risk of SMR were highest for patients aged < 60 years. CONCLUSION: Male breast cancer is of luminal subtype, but more often Luminal B. Ki67 is crucial in evaluation of subtypes by immunohistochemistry, but have limitations. Subtyping seems to be of major importance. AR also can have a role in future treatment. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12282-020-01066-3) contains supplementary material, which is available to authorized users.