Abstract
RATIONALE: Osteochondroma is a common benign bone tumor consisting of cartilage-covered bone confluent with the medullary canal of the epiphysis. Extraosseous osteochondroma shares the same appearance and histologic features as a typical osteochondroma but does not have any attachment to surrounding bone structures. Because of its low incidence, extraosseous osteochondroma is uncommon in clinical workups and thus prone to misdiagnosis. The diagnosis of extraosseous osteochondroma should be considered when there is a well-defined bony mass in the soft tissue with no direct continuity with the adjacent bone or joint. Here, we present a case of an imaging diagnosis of "calcified bursitis in the subcutaneous superficial fascial layer" and a postoperative pathological diagnosis of "extraosseous osteochondroma." PATIENT CONCERNS: The patient was a 61-year-old man who had a right plantar heel mass for 2 years and recently visited the hospital because of discomfort in shoes. DIAGNOSES: The patient was diagnosed with pathological examination. INTERVENTIONS: After completing the relevant preoperative examination and preoperative preparation and excluding contraindications to surgery, surgery was performed under nerve block anesthesia. OUTCOMES: We performed surgical resection, and the patient did not have obvious discomfort when discharged from the hospital. Auxiliary examination showed no abnormalities. LESSONS: For foot tumors, we need to consider the possibility of extraosseous osteochondroma. After completing the auxiliary examination, we should determine the relationship between the tumor and its surrounding tissues and blood supply before surgery to avoid causing major trauma.