Abstract A 72‐year‐old man with productive cough and wheezing was referred to our institution for a growing mass shadow and central bronchiectasis in the right lower lobe on computed tomography. Based on the symptoms, elevated Aspergillus‐specific immunoglobulin E levels, and radiological findings, allergic bronchopulmonary mycosis (ABPM) was suspected according to the Japanese clinical diagnostic criteria. The patient refused bronchoscopic examination, and oral prednisolone (0.5 mg/kg/day) improved the symptoms; however, the mass shadow continued to grow. Subsequently, bronchoscopy revealed mucus plugs and an endobronchial tumour with a whitish surface. The tumour was surgically resected, and the pathological diagnosis was a coexistence of ABPM and pulmonary pleomorphic carcinoma. To the best of our knowledge, this is the first case of ABPM developing at the site of pulmonary pleomorphic carcinoma. Careful bronchoscopic examinations and histopathological evaluations of the surgical specimen led to a prompt and accurate diagnosis.

A rare case of allergic bronchopulmonary mycosis complicating pulmonary pleomorphic carcinoma