Although much emphasis has been placed on the primary presentations of breast cancer, little focus has been placed on how systemic illnesses may affect the breast. In this article, we discuss systemic illnesses that can manifest in the breast. We summarize the clinical features, imaging, histopathology, and treatment recommendations for endocrine, vascular, systemic inflammatory, infectious, and hematologic diseases, as well as for the extramammary malignancies that can present in the breast. Despite the rarity of these manifestations of systemic disease, knowledge of these conditions is critical to the appropriate evaluation and treatment of patients presenting with breast symptoms.

Radiation therapy is an important and effective adjuvant therapy for breast cancer. Numerous health conditions may affect medical decisions regarding tolerance of breast radiation therapy. These factors must be considered during the decision-making process after breast-conserving surgery or mastectomy for breast cancer. Here, we review currently available evidence focusing on medical conditions that may affect the patient–provider decision-making process regarding the use of radiation therapy.

Male breast cancer is rare, and many patients and health care providers are not familiar with this entity. Although the underlying causes are not well understood, certain populations are at higher risk, including certain gene mutation carriers, men with Klinefelter syndrome, and certain ethnic groups. Male breast cancer typically presents at a later stage than female breast cancer. A palpable mass is the most common presentation, but nipple discharge or other nipple changes may be seen. Because the number of affected individuals is small, prospective trials have not been conducted; thus, treatment recommendations are typically taken from large trials involving female breast cancer populations. Although outcomes in male breast cancer were previously thought to be worse than female breast cancer outcomes, it appears that they are similar. Questions regarding the most effective surgical and adjuvant therapies remain. Mastectomy with axillary lymph node evaluation, adjuvant hormonal therapy, and chemotherapy are commonly used. Providers of health care to male patients must be aware of the possibility of breast cancer and appropriately evaluate any suspicious changes.