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Background
Radiologists may be less familiar with palpable breast masses in male patients relative to female patients. However, it is essential for radiologists to be familiar with the spectrum of male breast disease and know when to maintain an index of suspicion for male breast cancer.

Educational Goals / Teaching Points
By the end of this presentation, the viewer should be able to: Describe normal anatomic features of the male breast, Know the diagnostic approach for palpable abnormalities in the male breast, Characterize benign lesions in the male breast, Understand the imaging appearance of male breast cancers and be cognizant of potential benefits of screening in male patients at high-risk for breast cancer.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Normal breast tissue in males consists of primitive ducts, fat, and stroma. Of note, it does not contain lobules, so lobular pathologies such as cysts and lobular carcinoma are extremely uncommon in males. The first diagnostic imaging step in a patient with a palpable breast mass is typically mammography. Mammography is useful in identifying both gynecomastia and male breast cancers. In one study evaluating breast imaging utilization in 1869 men, mammography had 100% sensitivity, specificity, and positive predictive value in detecting male breast cancers. Some male palpable masses may initially be indeterminate. If a male patient < 25 years of age presents with an indeterminate breast mass, which does not fit clinically with gynecomastia, ultrasound is recommended. If a male patient > 25 year of age presents with an indeterminate breast mass, mammography is recommended. Benign Breast Masses: The most common cause of male breast pathology is gynecomastia. Common causes include medications, liver disease, or adolescent hormonal change. On mammography, gynecomastia has characteristic nodular, dendritic, and diffuse glandular morphologies. Pseudogynecomastia, increased fat deposition in the region of the breast, can also be seen. Benign pathologies associated with ductal tissue can present in men, such as intraductal papilloma. Etiologies such as eccrine tumors, epidermal inclusion cysts, and post-traumatic changes can also present as male breast masses. Male breast cancers: Male breast cancers account for <1% of all breast cancers, but the incidence of male breast cancer is projected to increase. Male cancers also often present at a later stage and thus can have poorer prognosis than female breast cancers. Male cancers often present with physical exam findings such as a palpable mass or skin or nipple changes. Imaging findings typically include a discrete mass on mammography and a hypoechoic irregular mass on ultrasound. Additionally, most male breast cancers are hormone-receptor positive and may benefit from hormonal-directed therapies. Some factors can increase risk of male breast cancers, and these patients may benefit from a targeted screening program.

Conclusion
Radiologists should be familiar with benign and malignant pathologies in the male breast and be cognizant of the potential benefit of breast cancer screening in men who are at high-risk.