Bronchoalveolar carcinoma as an unsuspected cause for worsening shortness of breath in a patient with metastatic breast cancer.

A 70-year-old woman with lung metastases from a breast cancer presented with worsening cough and dyspnoea. She recently had a pleurodesis for a malignant pleural effusion. Chest CT scans demonstrated various radiological changes leading to diagnostic challenges. Differential diagnoses included empyema, pleural disease progression, pulmonary oedema, pneumonitis, lymphangitis and atypical infections. She deteriorated despite a multimodality treatment strategy. Postmortem examination confirmed that lung changes were consistent with a bronchoalveolar carcinoma unrelated to the known metastatic breast cancer. The eventual knowledge of this diagnosis was reassuring to the treating medical team and a comfort to the relatives who witnessed the lack of response to standard treatment.