We present a case of pyoderma gangrenosum (PG) mimicking a lung carcinoma. A 52-year-old woman presented with an unremitting cough. Computed tomography revealed a cavitating lung lesion. Bronchoscopy and biopsy were interpreted as squamous cell carcinoma. Following a staging mediastinoscopy, a sleeve lobectomy and chest-wall resection was performed. The pulmonary histopathological features suggested Wegener's granulomatosis; no malignancy was found. Three months postoperatively, wound breakdown led to dermatological review. A clinical diagnosis of cutaneous PG was made on the basis of the classic appearance of the surgical wounds and an ulcer on the upper back that had been present before surgery. The patient has been consistently negative for cytoplasmic-staining antineutrophil cytoplasmic antibodies, which supports the diagnosis of PG with cutaneous and pulmonary involvement. Lung manifestations of PG are rare. PG is amenable to systemic therapy. Pulmonary PG is a rare but important differential diagnosis that is not familiar to many physicians and surgeons in this type of presentation.