Atypical lipomatous tumour (lipoma-like well-differentiated liposarcoma) arising in a pulmonary hamartoma and clinically presenting with pneumothorax.

We document an uncommon variant of pulmonary hamartoma (PH), discovered in the left upper lobe of a 60-year-old man after an episode of pneumothorax, a unique clinical presentation for such an occurrence. The tumour showed a prominent leaf-like pattern and was mainly composed of mature fat with adipocytes of different size and scattered throughout lipoblasts and floret-like cells. A lobectomy was performed and more than 7 years after surgery the patient's course is still uneventful. This case represents an exceedingly rare example of an histologically malignant change in PH and bears a close clinicopathologic resemblance to atypical lipomatous tumours of soft tissues.