Breast cancer is the leading cause of skin metastasis in women with internal malignancies. This report highlights an atypical case of cutaneous metastasis of breast cancer (CMBC) in a 66-year-old woman. Starting four months before her dermatology consultation, the patient underwent a chemotherapy regimen comprising pertuzumab, trastuzumab, and vinorelbine for right breast cancer, right axillary lymph node enlargement, and bone metastases. After commencing chemotherapy, erythematous macules appeared around her right nipple. Subsequently, the cutaneous lesions developed into annular erythematous patches around her right nipple and began to coalesce and expand to the contralateral breast. A skin biopsy revealed dysplastic cells indicative of metastasis from invasive ductal carcinoma. In addition, lymphovascular tumor cell invasion was noted in the reticular dermis. Based on these clinical progressions and histopathologic findings, a diagnosis of CMBC was made, specifically considering the possibility of inflammatory breast cancer (IBC). The patient continued the same chemotherapy regimen for 17 cycles, which improved the skin lesions, but she succumbed to breast cancer two years later. This case emphasizes the importance of considering CMBC in breast cancer patients with expanding, treatment-resistant thoracic cutaneous lesions, especially in aggressive subtypes like IBC. The diverse presentations of CMBC require thorough histopathological evaluation.
Keywords: annular erythema; breast cancer; cutaneous metastasis of breast cancer; erythema annulare centrifugum; skin metastasis.
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