A Subdermal Osteochondroma in a Young Girl.

Osteochondromas are common benign tumors of cartilage and bone. They are usually found as contiguous bone with a cartilage cap at the end of the growth plate of long bones. Similar to structure are extraskeletal osteochondromas. However, unlike typical osteochondromas, extraskeletal osteochondromas are noncontinuous with bone. To our knowledge, all reported extraskeletal osteochondromas have been contained within fascial compartments. Here we present the case of a 5-year-old female who had a slow growing mass of the anterior distal right thigh. Imaging studies revealed an ossified mass extending from dermal layer of the subcutaneous tissue with no connection to the underlying deep fascia. An excisional biopsy was performed and proved to be a subdermal extraskeletal osteochondroma.