Triple-Negative Breast Cancer with Dermatomyositis: A Case Report and Literature Review

Purpose: Dermatomyositis (DM) is an autoimmune inflammatory myopathy, the onset of which is sometimes associated with some malignancies and sometimes appears as a symptom of paraneoplastic syndrome. The main symptoms include progressive proximal muscle weakness, extra muscular manifestations such as dyspnea or dysphagia, and skin changes. There is currently no standardized treatment for breast cancer associated with DM. Patients and Methods: We report a 45-year-old woman with a palpable mass over the left external breast along with diffuse erythema on the shoulder, orbital edema, voice hoarseness, dyspnea, and weakness of the extremities. Needle aspiration biopsy and imaging suggested malignancy. Thus, breast-conserving surgery and pectoral myotomy biopsy+ skin excision biopsy were performed. Pathology confirmed triple-negative breast cancer (TNBC) and DM. Two days after surgery, the patient's orbital edema, voice hoarseness, dyspnea, and weakness of the extremities were significantly reduced, and the erythema subsided significantly. Left axillary lymph node dissection was performed after postoperative adjuvant chemotherapy, and the nodes were negative. The patient was recovering well, and follow-up showed no signs of recurrence or metastasis. Conclusion: Be alert for the presence of malignancy when a breast cancer patient presents with DM, a test for dermatologists, rheumatologists, and oncologists. This case demonstrated the effectiveness of breast-conserving surgery combined with radiotherapy for early-stage triple-negative breast cancer with DM, even without further treatment for DM to reduce the symptoms. In conclusion, the treatment plan for these patients depends on the presentation of the tumor and DM.