Metastases after mastectomy for ductal carcinoma in situ of the male breast; A case report.

Introduction: and importance: Male breast cancer is a rare entity. Ductal carcinoma in situ (DCIS), constituting 10% of all male breast cancer, is confined within the breast ducts and lobules, rarely metastasizing and even less so after mastectomy. Case presentation: A 71 years old male with no history of trauma presented with pain, swelling, and deformity of the left arm. He had continuous back pain for 6 months and a history of mastectomy of the right breast. Fracture of shaft of the left humerus was detected on X-ray. Computed tomography (CT) showed multiple vertebral metastases later confirmed to be metastasized from the breast by biopsy. Tumor cells were progesterone receptor (PR) positive, estrogen receptor (ER) negative, and human epidermal growth factor receptor 2 (HER2) negative. The fracture was treated and the patient was kept on Tamoxifen. On follow-up after four months, the patient is doing well with relief of back pain. Clinical discussion: Despite mastectomy and the histopathological diagnosis of pure DCIS, distant metastases can occur even in absence of locoregional recurrence. Therefore, the aggressive phenotype of DCIS rather than diagnostic or treatment variables can be thought to bring worse outcome in the form of metastases. Early hormonal status identification and hormone therapy could result in a better outcome. Conclusion: Skeletal metastases should be strongly suspected in patients presenting with bone pain and having a history of DCIS of the breast, even after mastectomy. Even though distant metastasis after mastectomy is rare, regular follow-up and surveillance is necessary.