Background: Osteoblastoma and osteoid osteoma are rare, benign, bone forming tumours. This is a rare case of osteoblastoma in shaft of a long bone, in an unusual location, causing a therapeutic dilemma.
Aims & Objectives: Osteoblastoma and osteoid osteoma are closely related lesions with similar histological patterns and indistinguishable radiographic features. This case was studied to understand the similarities and differentiating features of the two.
Methods: Here was a case of 18 years old male patient with history of bony swelling and pain in his right leg which relived with a dose of Aspirin. After thorough examination plain radiographs and CT scan of the part was done. Surgical excision of the lesion was done and sent for histopathology examination. Patient was adequately treated and followed up at 1,3,12 & 18 months post operatively to assess the involved site and evidence of recurrence.
Result: Plain radiographs and CT scan of the part involved provisionally diagnosed the lesion as osteoid osteoma. Histopathology examination found features suggestive of osteoid osteoma and a diagnosis of osteoblastoma was given, considering the size of the nidus. Patient was followed up at 1,3,12 & 18 months post operatively and there was no evidence of recurrence.
Conclusion: Osteoblastoma and osteoid osteoma were classified as variants of single tumour type based on a number of shared histological and radiographic features. Most significant difference between the two lesions is the size of the nidus. Thus, there may be transitional zone of uncertainty in establishing the correct diagnosis. Osteoid osteoma must be considered a differential diagnosis when the lesions are large and in unusual sites like long bones.