Can an exostosis be free floating without any continuity to the underlying bone: A diagnostic dilemma

Osteochondroma or exostosis is the most common primary bone tumor containing both bone and cartilage. Soft tissue osteochondromas have been described at various locations, however, to the best of our knowledge, there is only a single case report of a soft tissue osteochondroma around the femoral neck. We, hereby report second such case.

A forty year old female presented with swelling on medial aspect of left thigh since four years. Radiographs showed a large mass at the inferior surface of the left femoral neck. CT scan revealed a well defined lobulated mass lesion involving muscles of adductor compartment of thigh. MRI showed lobulated periarticular, intramuscular, non enhancing lesion isointense to the bone, but without any continuity to the adjacent femur. Histopathology of the excised lesion turned out to be osteochondroma with origin from soft tissue. This case highlights an important differential diagnosis to be considered whenever an ossified mass is located in soft tissue.