Osteosarcoma of the bones of the foot--an easily misdiagnosed malignant tumor.

OBJECTIVE: To evaluate the frequency of osteosarcoma involving the foot and determine the clinical outcome of affected patients.
MATERIAL AND METHODS: We retrospectively reviewed the cases of osteosarcoma encountered between 1911 and 1992 at the Rizzoli Orthopedic Institute. In particular, we analyzed whether common clinical, radiographic, or histologic features could lead to a correct diagnosis of osteosarcoma of the foot.
RESULTS: The bones of the foot were the primary site of osteosarcomas in 12 cases--0.6% of the entire series of such tumors at our institution during the study period. The mean age of the patients was 33 years. Initial symptoms were usually pain and swelling. Late diagnosis was common; the mean time interval between the first symptoms and diagnosis was 28 months. Misdiagnoses occurred in 6 of the 12 cases (50%): osteoblastoma, chondroblastoma, chondrosarcoma, osteoid osteoma, desmoid fibroma, and osteomyelitis were, respectively, the initial diagnoses. Histologically, 5 of the 12 tumors (42%) were low-grade lesions. Four of the seven patients with a high-grade tumor died of metastatic disease after a mean survival of 50 months. Eight patients are alive with no evidence of disease after a mean follow-up of 162 months.
CONCLUSION: When a painful swelling in a bone of the foot is observed, even if numerous benign conditions (such as fractures, infections, or benign bone tumors) are far more likely to occur, osteosarcoma must be ruled out to avoid delays in the treatment. Osteosarcomas of the foot may easily be misdiagnosed, especially because they almost always occur in adults, in contrast to osteosarcomas in general. High-grade tumors of the foot are as aggressive as other osteosarcomas and should be managed accordingly--with use of a safe-margins surgical procedure and chemotherapy.