Introduction 1 4 9 15 17 20 28 7 14 7 2 6 7 18 21 22 24 27 13 13 26 3 7 8 12 19 22 25 In this study, we investigated the frequencies and distribution of the various histologic subtypes in a large data set of invasive carcinomas seen at a large tertiary center over a 40-year period. Our goals are to document these frequencies and distribution and to see whether any histologic subtypes are notably distinct in frequency of occurrence in the male breast, as compared with historical published data on similar lesions in the female breast. The frequencies and sites of origin of metastatic tumors to the male breast during the study period were also investigated. Materials and methods n 23 n n 13 19 Results 1 1 infiltrating duct carcinoma not otherwise specified n n 1 Table 1 Distribution of the various histologic subtypes in 778 invasive carcinomas involving the male breast Histologic subtype Number of cases Percentage a 643 84.7 Carcinoma associated with Paget’s disease 34 Carcinoma with prominent apocrine features 17 Carcinoma with medullary features 4 Carcinoma with osteoclast-like giant cells 3 Carcinoma with focal signet rings 2 Carcinoma with focal clear cells 2 Pleomorphic carcinoma 2 Carcinoma with no notable distinctive features 579 Papillary intraductal carcinoma with invasion in the form of infiltrating duct carcinoma 34 4.48 Mixed infiltrating duct and mucinous carcinoma 26 3.4 Pure mucinous carcinoma 21 2.8 Adenoid cystic carcinoma 8 1.05 Tubular carcinoma 6 0.8 Small cell carcinoma 6 0.8 Invasive lobular carcinoma 3 0.39 Solid neuroendocrine carcinoma 3 0.39 Mixed lobular and ductal carcinoma 3 0.39 Adenocarcinoma with spindle cell  metaplasia 2 0.26 Pure signet ring carcinoma (no in situ component) 1 0.13 Invasive cribriform carcinoma 1 0.13 Secretory carcinoma 1 0.13 Squamous cell carcinoma 1 0.13 Total 759 100 Metastatic lesions 19  Final total 778  a Fig. 1 a b b c mucinous right field left field d e f e f  Discussion 13 13 In this study, we investigated in detail the frequencies and distribution of the various histologic subtypes in a large data set of invasive carcinomas seen at a large tertiary center over a 40-year period. Our findings suggest that invasive carcinoma of the male breast displays a morphologic spectrum and distribution of histologic subtypes that is comparable to invasive carcinoma of the female breast and that no specific histologic subtypes are notably over- or underrepresented with the exception of papillary and lobular variants. 1 5 7 p 11 10 16 8 7 In summary, invasive carcinoma of the male breast appears to display a morphologic spectrum and distribution of histologic subtypes, which is comparable to invasive carcinoma of the female breast with some variation. As expected, lobular carcinoma is exceedingly rare but was encountered in this series. There appears to be a twofold increase in the frequency of invasive papillary carcinoma and metastatic cancers to the male breast as compared to published data in the female breast. Finally, the most common tumor metastatic to the male breast in this series was cutaneous melanoma.