Lung carcinoma mimicking hydatid cyst: a case report and review of the literature.

It is unusual for a malignant lung tumor to present clinically as a cystic lesion. A case of large cell carcinoma of the lung mimicking pulmonary hydatid cyst is reported herein. The patient was a 65-year-old male who presented with history of slowly progressive breathlessness and painful swelling over the left chest wall. Computed tomography of the chest showed a well defined cystic lesion in the left upper lobe with outward extension through the left 2nd-3rd intercostal space in the absence of bony destruction. The patient was found to have positive serological test for Echinococcus granulosus and therefore the preoperative diagnosis was that of complicated pulmonary hydatid cyst. Intra-operative findings included presence of a large cavity filled with necrotic material and "daughter cysts". Dense adhesions between the cavity wall and the thoracic cage prevented complete surgical resection. Histopathological evaluation of the excised specimen showed large cell carcinoma. The case highlights the fact that a lung carcinoma may rarely have clinical, radiological, and serological features similar to those of a pulmonary hydatid cyst.