Lung cancer masquerading as breast cancer with carcinoma en cuirasse

Metastases to the breast from lung cancer are rare. Carcinoma en cuirasse is an unusual form of metastatic cutaneous carcinoma, almost exclusively described as deposits secondary to breast carcinoma. A 63-year-old woman presented with dyspnoea. A CT scan demonstrated a pleural effusion, large pericardial effusion, mediastinal lymphadenopathy and right basal consolidation. Pleural fluid cytology and immunohistochemistry were consistent with a diagnosis of primary lung adenocarcinoma. The patient was treated with pemetrexed and carboplatin, resulting in stable disease. A year later, she developed bilateral breast masses and multiple painful erythematous subcutaneous nodules over her torso, clinically indistinguishable from carcinoma en cuirasse. A biopsy demonstrated these were deposits from metastatic adenocarcinoma of the lung. The patient received docetaxel and carboplatin with initial good response. The painful lesions were subsequently treated with radiotherapy, which provided symptomatic relief. To the best of our knowledge, this is the only case of metastatic lung adenocarcinoma mimicking carcinoma en cuirasse.