May2006: Letters to the Editors

Diagnosis of hydatid disease (HD) is usually based on its clinical and radiologic presentation. However, radiologic appearances of bone lesions are nonspecific and mimic inflammatory diseases and neoplasms.6 Despite limited experience with fine needle aspiration biopsy (FNAB) in the evaluation of cystic bone lesions, HD is diagnosed in cytology.1-5 A 33-year-old woman presented with right hip pain for the previous 4 months. Radiologic findings were not diagnostic but conclusive about an inflammatory or neoplastic lesion limited to the iliac bone. FNAB revealed a highly viscous, yellowish liquid. On microscopy, rare osteoclastic multinucleated giant cells in a hemorrhagic background were detected. The cytologic diagnosis was inconclusive, and tissue biopsy was recommended. The preoperative clinical diagnosis included HD. The histopathologic diagnosis was HD. Review of the FNAB slides revealed a few fragments of acellular, laminated membranes (Figure 1). Primary osseous HD infestation, particularly of pelvic bones, is rare, occurring in 0.5–4% of cases.6 A conclusive preoperative diagnosis is possible in only half the cases.2 The differential diagnosis includes chondromyxoid fibroma, malignant fibrous histiocytoma, multiple myeloma, giant cell tumor, aneurysmal bone cyst, tuberculosis and metastases. Despite previous reports of spillage of cystic fluid, leading to anaphylactic shock or dissemination of disease, FNAB has been used rather safely in many cases of HD for diagnostic and/or therapeutic purposes.1,2,4,5 The cytopathologic characteristics are protoscolices, hooklets and/or fragments of the acellular laminated membrane. Osteoclastic giant cells are also seen in many lytic and neoplastic bone lesions and are not diagnostic alone. In FNAB of bone lesions, osteoclastic giant cells scattered in a hypocellular or hemorrhagic background should alert the cytopathologist to search for other findings diagnostic of HD. Laminated membranes should not be neglected as they might be the only diagnostic clue to the diagnosis.