Track: Case Reports

Abstract:

Occult breast cancer (OBC) is a rare subtype of breast cancer, comprising 0.3–1% of cases, and presents as metastatic disease from an undetectable primary breast tumor. This report describes a 48-year-old woman who presented with a painless rash in her right axilla for two months. It was initially clinically diagnosed as psoriasis and treated with a steroid cream. Examination revealed a well-demarcated, flesh-colored to red, firm, painless plaque with a velvety surface and multiple satellite papules. Skin biopsy demonstrated intralymphatic cutaneous metastases characterized by pleomorphic, mitotically active neoplastic cells within dermal lymphatic vessels, and neoplastic cells demonstrated notable necrosis. Progressively, she developed swelling of the right upper limb with numbness, burning sensation, and weakness. Further evaluation, including chest X-ray, mammography, breast and abdominopelvic ultrasound, were negative; head and neck CT scan showed right axillary and cervical lymphadenopathy. Immunohistochemistry of a lymph node biopsy showed HER2/neu positivity and ER/PR negativity, consistent with secondary ductal carcinoma. The diagnosis of HER2-positive occult breast cancer with cutaneous metastasis was made. The patient underwent six cycles of chemotherapy with doxorubicin, cyclophosphamide, and paclitaxel, resulting in significant clinical improvement of both the skin lesions and upper limb symptoms. This report underscores the importance of considering cutaneous metastases in patients even without a known primary malignancy and emphasizes the essential role of biopsy of suspicious or unexplained skin lesions. Early recognition and appropriate oncologic management is essential to improve outcomes in such atypical presentations.

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Lishan Tefera