Imaging findings and classification of the common and uncommon male breast diseases

Male breast hosts various pathological conditions just like "female breast." However, histo-anatomical diversities with female breast lead to many differences regarding the frequency and presentation of diseases, the radiologic appearance of lesions, the diagnostic algorithm, and malignity features.Radiological modalities may play an important role in evaluating male breast lesions. Although some imaging findings are non-specific, having knowledge of certain imaging characteristics and radiologic patterns is the key to reduce the number of differential diagnoses or to reach an accurate diagnosis.Male breast imaging is mostly based on physical examination and is required for the complaints of palpable mass, breast enlargement, tenderness, nipple discharge, and nipple-skin changes. The majority of the male breast lumps are benign and the most common reason is gynecomastia. Although it is difficult to exclude malignancy in some cases, gynecomastia often has distinguishable imaging features. Pseudogynecomastia is another differential diagnosis that may be confused with gynecomastia. The distinction is important for the treatment plan.Apart from gynecomastia, other male breast lesions form a highly heterogeneous group and can be classified based on "Tissue origin," "Histopathological type and behavior," and "Radiologic features" for both simplification and comprehensive understanding.This article mainly focuses on emphasizing the results of basic histo-anatomical differences of male and female breasts, classifying male breast lesions, covering the spectrum of male breast diseases, and assisting radiologists in recognizing the imaging findings, in interpreting them through a holistic approach, in making a differential diagnosis, and in being a part of proper patient management.