Breast cancer is an uncommon disease in men. As a result, the diagnosis may not initially be considered. Understanding the common benign and malignant entities affecting the male breast is critical for timely and accurate diagnosis in the primary care setting. Most patients present with a palpable breast mass or pain. The usual etiology is gynecomastia, the most common breast condition in males, but breast cancer must always be excluded through careful imaging evaluation when physical examination findings are suspicious or inconclusive. Imaging of the male breast generally relies on mammography and ultrasound, with mammography employed as the initial imaging modality of choice and ultrasound when a mass is detected or suspected. Here we describe the normal male breast anatomy and present an evaluation algorithm for the male patient with breast signs or symptoms. The most common benign and malignant entities are described.
Normal Male Breast Anatomy
Until puberty, the male and female breasts are identical, composed of fibrofatty tissue and ducts lined by a single layer of epithelial cells with an underlying layer of myo-epi-thelium. During puberty, testosterone levels increase in males, causing involution and atrophy of the ducts. As a result, the normal adult male breast is primarily composed of subcutaneous fat, stromal elements, a small nipple-areolar complex, and an underlying, poorly developed ductal system that ends blindly. The presence of terminal duct lobular units is rare and Cooper ligaments are absent. This is distinctly different from the female breast, in which ducts, stroma, and glandular tissue predominate.
Mammographically, the normal male breast is homogeneously radiolucent, with a prominent pectoralis muscle seen posteriorly (Figure 1A and B). Ultrasound anatomy of the normal male breast consists mainly of subcutaneous fat and skin (Figure 1C).
Clinical and Imaging Evaluations
The most common presenting breast symptoms in male patients are a palpable lump, tenderness, and enlargement. Breast physical examination in men has been reported to be very sensitive, but lacks specificity in the detection of malignancy. In their study of 628 male patients, Muñoz Carrasco et al reported a positive predictive value of 19.2% and a negative predictive value (NPV) of 99.5% for breast physical examinations. Other studies have reported a sensitivity of 85%-100%, a specificity of 89%-95.3%, and a positive predictive value of 8%-55%. Therefore, findings on physical examination suspicious for malignancy warrant further evaluation with imaging, while normal or benign physical examination findings generally do not require an imaging evaluation. As in women, the principal imaging tools are mammography and ultrasound. In their study, Muñoz Carrasco et al reported a sensitivity of 94.7%, a specificity of 94.8%, and an NPV of 99.7% for mammography and a sensitivity of 88.9%, a specificity of 95.3%, and an NPV of 99.4% for ultrasound.
Given its high sensitivity, mammography is the recommended initial imaging modality to further evaluate suspicious or indeterminate physical examination findings. Because risk factors predisposing for male breast cancer affect both breasts, bilateral mammogram should always be performed. The standard mediolateral oblique and craniocaudal views should be obtained. Magnification or spot compression mammographic views may be obtained as needed (Figure 2A-D).
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-Alec Chau, MD, Neda Jafarian, MD, Marilin Rosa, MD
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This article originally appeared in the August 2016 issue of The American Journal of Medicine.
