Primary soft tissue hydatidosis: aspiration cytological diagnosis in two cases.

The most common sites of cysts caused by hydatid disease are liver and lung. In the absence of visceral involvement, the disease rarely affects musculoskeletal and soft tissues. In such locations, hydatid cyst mimics commoner soft tissue tumors. A 12-year-old girl presented with a gradually increasing painless right shoulder swelling. With a clinical diagnosis of lipoma, fine needle aspiration cytology was performed, which showed cytomorphological features of a hydatid cyst. Another patient, a 20-year-old man, presented with a right paravertebral soft tissue swelling. Radiological investigations did not reveal any bony abnormality or features of intervertebral disc prolapse and thus, a clinical diagnosis of a paravertebral soft tissue tumor was considered. Fine needle aspiration from the soft tissue swelling showed laminated membrane, compatible with hydatid cyst. No visceral involvement was detected in either of the cases. Parasitic cysts, although rare, should be kept in the list of cytological differential diagnosis of soft tissue lesions. Occurrence of hydatid cyst in a soft tissue location is extremely rare. Aspiration cytology can be used efficiently in the diagnosis without the risk of spillage of contents. (c) 2008 Wiley-Liss, Inc.