Osteochondromas are common and typically arise from the metaphyseal ends of long bones. An osteochondral neoplasm of the soft tissue, which is a lesion of uncertain pathogenesis, is uncommon and usually arises from the synovial tissue in joints and tendon sheaths. Rarely, extraskeletal osteochondromas also arise outside of synovial compartments. Most of the reported cases were presented in the hands and feet, especially in the fingers. Here we describe a 44-yr-old female patient who presented with a pain in the left buttock. A well-defined osseous mass was detected in the buttock. It consisted of sharply demarcated, mature hyaline cartilage that was covered with a fibrous capsule, which changed gradually into cancellous bone, more pronouncedly at the center. The diagnosis of an extraskeletal osteochondroma should be considered when a discrete, ossified mass is localized in the soft tissues. A case of pathologically proven extraskeletal osteochondroma of the buttock is presented with a literature review, magnetic resonance imaging, and radiological findings.
Accidental Falls ; Adult ; Buttocks* ; Diagnosis, Differential ; Female ; Human ; Myositis Ossificans/diagnosis ; Osteochondroma/complications ; Osteochondroma/diagnosis* ; Osteochondroma/radiography ; Osteochondroma/surgery ; Pain/etiology ; Sarcoma/diagnosis ; Soft Tissue Neoplasms/complications ; Soft Tissue Neoplasms/diagnosis* ; Soft Tissue Neoplasms/radiography ; Soft Tissue Neoplasms/surgery

Here, we describe a popliteal mass that was initially misdiagnosed as a simple popliteal cyst, which finally turned out to be osteochondrolipoma. A 63-year-old housewife presented with sustained knee pain in association with a palpable mass on the popliteal fossa. The mass was in the posteromedial area and soft, non-tender, non-movable in the posteromedial area. Using plain radiography, the mass appeared as a round, soft tissue density lesion containing bony fragments. We performed an ultrasound-guided needle biopsy in conjunction with magnetic resonance imaging, followed by an open excisional biopsy. Microscopically, histological sections showed a lipoma with cartilaginous and osseous differentiation, finally diagnosed as osteochondrolipoma. In conclusion, popliteal masses are not always simple cysts, and the evaluation of masses in the popliteal fossa is always necessary.
Female ; Humans ; Lipoma/complications/*diagnosis ; Middle Aged ; Osteochondroma/complications/*diagnosis ; Popliteal Cyst/etiology ; Soft Tissue Neoplasms/complications/*diagnosis

Aged ; Ankle Injuries ; complications ; Bone Neoplasms ; complications ; Fibula ; injuries ; Fractures, Spontaneous ; etiology ; Humans ; Ligaments, Articular ; injuries ; Male ; Osteochondroma ; complications ; Tibia