When the Skin Becomes Armor: Carcinoma En Cuirasse revealing breast cancer progression

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Carcinoma en cuirasse is a rare form of cutaneous metastasis associated with advanced breast cancer, characterized by diffuse sclerodermoid induration of the skin. We report the case of a 50-year-old woman treated for invasive ductal carcinoma of the left breast, who presented seven years later with pulmonary metastases and a progressively evolving erythematous, indurated plaque of the anterior chest wall, associated with infiltrated papules and a peau d'orange appearance. Skin biopsy showed infiltration of the dermis and hypodermis by malignant epithelial cells arranged in cords and trabeculae within a fibrous stroma. Immunohistochemistry confirmed metastatic invasive ductal carcinoma, with strong positivity for GATA3, E-cadherin, and estrogen receptors in approximately 90% of tumor cells, consistent with a grade II invasive ductal carcinoma (Elston and Ellis classification). Carcinoma en cuirasse is a rare but characteristic manifestation of breast cancer progression that frequently mimics benign dermatoses or post-radiotherapy changes, and its diagnosis relies on histopathological examination. This case underscores the importance of recognizing cutaneous metastases in patients with a history of breast cancer, since their presence signals advanced disease and carries significant implications for management.