Aggressive osteoblastoma of the calcaneus.

Aggressive osteoblastoma of the left calcaneus in 29-year-old Japanese woman is reported. Her initial symptom was heel pain while walking. This was a primary calcaneal tumor, initially diagnosed as a benign osteoblastoma. After a 5-year follow-up (from the initial curettage), there was local recurrence. The histologic findings of aggressive osteoblastoma were confirmed after right lower leg amputation. The recurrent tumor was mildly aggressive to the talocalcanean joint and the retrocalcaneal area, without distant metastasis. The characteristics of the primary and recurrent tumors were examined by the radiologic, histologic, and electron microscopic procedures. Although there are questions about aggressive osteoblastoma, the authors believe that there are osteoblastic tumors of borderline malignancy between benign osteoblastoma and low-grade osteosarcoma. The current case was an example compatible with an aggressive osteoblastoma with the proposed name of Dorfman classification Group 4.