Publication:

When a skin lesion imitates a metastatic breast cancer: a diagnostic pitfall

Adenocarcinoma involving the skin presents a diagnostic challenge, as it may represent either a rare primary cutaneous adnexal malignancy or cutaneous metastasis from an internal primary, most commonly breast carcinoma. We report the case of a 77-year-old female with a scalp lesion excised for presumed squamous cell carcinoma (SCC), with an immunohistochemical profile raising concern for metastatic breast carcinoma. Despite a strong family history of breast cancer, comprehensive systemic investigation with various imaging modalities, tumour markers, and screening mammograph identified no primary malignancy. Surgical re-excision was performed to achieve clear margins, and final histopathology demonstrated a small residual focus of adenocarcinoma with negative margins. In the absence of an identifiable visceral primary, findings were most consistent with primary cutaneous adnexal adenocarcinoma. This case emphasises the importance of a multidisciplinary approach and supports complete surgical excision with margin clearance as definitive management when metastatic disease is excluded.