A 55-year-old man presents with a solitary breast mass and biopsy reveals malignant cells. Immunohistochemical staining experiments show that the tumor cells are positive for HER2/neu and cytokeratins 4 and 11 and negative for estrogen receptors. Which of the following is thought to play a role in the development of cancer in the patient?

Predisposing factors for the development of breast cancer in men are largely unknown, although mutations in the BRCA2 gene increase the risk of this tumor. Choices B, C, and D are not risk factors for breast cancer in men. PTEN mutations (choice E) are associated with endometrial intraepithelial neoplasia and endometrial adenocarcinoma.Diagnosis: Male breast cancer