This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breast, Subject name: Pathology
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? 
Select and explain. 
A. BRCA2 mutation, B. Chronic alcoholism, C. Gynecomastia, D. Hyperestrinism
A: BRCA2 mutation
Answer: A: BRCA2 mutation 
Explanation: 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