Giant extraskeletal osteochondroma of the plantar midfoot arch.

Osteochondromas found within the soft tissue without osseous or intra-articular involvement are better described as extraskeletal osteochondromas. They are slow-growing, benign, osseous tumors, and are often misdiagnosed as conventional osteochondromas. Though extraskeletal osteochondromas are rare, they typically affect the digits of the hands or feet. We present a patient with a giant symptomatic extraskeletal osteochondroma that developed in the plantar medial longitudinal arch of the foot. To the authors' knowledge, this is the largest isolated extraskeletal osteochondroma in the arch of the foot identified in the literature. The diagnosis of an extraskeletal osteochondroma should be considered when a well-defined osseous mass occurs in the soft tissue.