Abstract: Occult breast cancer is defined by the presence of axillary metastases without an identifiable primary breast tumor. Here, we report a rare case of a male occult breast cancer with dermatomyositis. We performed a modified radical mastectomy consisting of whole breast mastectomy and axillary lymph node dissection. Immunohistochemistry and fluorescent in situ hybridization analyses demonstrated an adenocarcinoma likely of breast origin, which was an occult triple-negative breast cancer. Interestingly, the patient’s previously noted periorbital dermatomyositis resolved promptly following surgical excision.

Keywords: male breast cancer, occult breast cancer, triple-negative breast cancer, dermato­myositis 

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Occult breast cancer (OBC) is defined by the presence of axillary metastases without an identifiable breast tumor. It has been reported that most hormone receptor (HR)-positive rate of male breast cancer (MBC) is higher than that of female breast carcinomas. We encountered a unique case of OBC, the immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH) studies of which was a triple-negative breast carcinoma (TNBC). Interestingly, the patient developed periorbital erythematous papules 3 months before diagnosis of MBC. This was suspected to be dermatomyositis (DM), which has not been reported in male OBC patients previously. The purpose of this study is to describe and discuss the diagnosis, the clinicopathologic characteristics, and treatment of this rare subtype of breast carcinoma.


In May 2015, an 84-year-old male patient who denied any history of smoking or alcohol consumption, with no family history of breast cancer, discovered a palpable nodule in his right axilla. An ultrasound examination confirmed an irregular hypoechoic solid mass in the right axillary cavity measuring 3.9 cm in the longest diameter (Figure 1). Color Doppler signal demonstrated internal vascularity with absent fatty hilum. A core needle biopsy revealed a poorly differentiated adenocarcinoma (Figure 2), which was likely of breast origin. Three months before presentation to our department, the patient had developed periorbital erythematous papules, distributed over the lower eyelids, measuring 2.0×1.5 cm (Figure 3), which was diagnosed as DM by the rheumatology department. Over the subsequent 3 months, he had also noted progressive proximal upper muscle weakness in a symmetric distribution. However, he declined any therapeutic intervention.

Physical examination identified a nonmobile mass in the right axilla, measuring 5.0 cm in diameter; other superficial lymph nodes were not significantly enlarged and the skin covering the mass was normal. No nipple discharge and no masses were identified in either breast or other organs. A computed tomography scan of the brain, abdomen, and pelvis failed to reveal any malignant primary lesions. The bone scan screening for metastasis was negative.