A 58-year-old woman with dry cough and progressive dyspnea on exertion in spite of various antitussive therapies, including herbal medicines in a family clinic, visited our hospital. She was receiving adjuvant chemotherapy and radiotherapy for postoperative breast cancer (pT4N3aM0, stage IIIc) six months before. She was diagnosed as drug-induced pneumonia or radiation-recall pneumonitis caused by various drugs, including herbal medicine based on the bilateral small ground-glass opacity of chest CT findings and KL-6 elevation. Two weeks after the initiation of steroid therapy, she was admitted to our hospital because of the appearance of pleural effusion; then she was diagnosed as recurrent breast cancer by immunostaining of cell-block-method specimens by chest drainage. Although her dyspnea was improved for a while after chemotherapy, she died of subacutely progressive respiratory failure on hospital day 42. Autopsy findings revealed pulmonary tumor thrombotic microangiopathy (PTTM), but radiation pneumonitis was not detected.