Aggressive Osteoblastoma Involving the Navicular Bone of Foot: A Rare Tumor in a Unique Location.

Abstract

Aggressive osteoblastoma (AO) is a rare variant of osteoblastoma characterized histologically by epithelioid osteoblasts and clinically by local recurrences if not excised completely. Aggressive osteoblastoma has been described in various unusual sites; however, based on our search of the literature, involvement of the tarsal navicular has not been previously described. Herein, we report what we believe to be the first case of aggressive osteoblastoma involving the tarsal navicular in a 35-year-old woman. The tumor showed osteoid surrounded by epithelioid cells along with numerous osteoclastic giant cells. Absence of necrosis, mitosis, and infiltration into the surrounding native bone helped rule out the possibility of low-grade osteosarcoma.