A 28-yr-old female presented 2 weeks after an uneventful delivery by Caesarean section with progressive cough, dyspnoea and left-sided chest pain. Medical history was uneventful but she had smoked until her pregnancy (16 pack-yrs). On admission, conventional chest radiography revealed a large pulmonary mass in the left lung ( fig. 1a). A computed tomography (CT) scan showed a large, slightly inhomogeneous mass in the upper lobe of the left lung ( fig. 1b). Apart from a 17-mm lesion in the left pulmonary vein, no other metastases were found. CT-guided true-cut biopsy was not diagnostic, and so a thoracotomy was performed. In the frozen section, a malignant process was diagnosed, and the surgeon proceeded to a left upper lobectomy and mediastinal lymphadenectomy.