Osteochondroma versus Chondrosarcoma a Diagnostic Dilemma - a Case Report

Osteochondroma is a benign bone tumor, commonly seen as a bony outgrowth from the metaphysis of long bones, having a stalk and cartilage cap. They may be sessile or multiple and usually arise before 20 years of age with no growth beyond puberty. Malignant transformation is a rare complication seen in 1% of solitary cases and 3-5% in the hereditary multiple enchondromatosis variety. Here, we report a rare case of atypical benign osteochondroma with clinical and radiological features suggestive of a malignant transformation.

A 17-year-old boy presented to us with a complaint of swelling in his right thigh for 12 years. Radiological features were suggestive of malignant transformation, with bony outgrowth exhibiting heterogeneous calcification, local invasion, and a cartilage cap of size 2.5 cm. Bilateral lung nodules were detected on high-resolution computed tomography. Positron emission tomography scan showed no evidence of metastasis. The patient underwent a wide excision of the tumor and the histopathology revealed it to be a benign osteochondroma. It is an atypical presentation of osteochondroma in which we had a discrepancy in radio-histopathological correlation.

In instances of diagnostic uncertainty concerning atypical osteochondroma, opting for an excisional biopsy serves as a prudent next step for the planning of subsequent management. The patient needs to be followed up regularly to look for recurrence or any other signs of metastasis.