Primary hydatidosis of distal femur masquerating malignancy-a rare case

 Hydatidosis of bone is a very rare condition and its incidence as compared to other organs range from 0.5-4%. There is no typical clinical appearance and the image characteristics on Xray and CT are similar to those of tuberculosis, metastasis, giant cell tumour or bone cyst. Case Summary- A 53 year old female presented to the orthopaedics OPD of Safdarjung hospital with pain and swelling over her right knee region. Routine radiograph exhibited multiple lytic lesions with thinned out cortices and fracture of supracodylar region. A provisional clinical diagnosis of malignancy was made and fine needle aspiration was advised. Cytology was reported as suspicious of malignancy and histopathology was asked for confirmation. Biopsy was reported as Hydatid disease of bone. Early diagnosis is uncommon in primary hydatidosis of bone as it is not considered in the differential diagnosis of osteolytic lesion. Long term survival is possible with early diagnosis. This case is being presented due to its rarity.