Subcutaneous extraskeletal osteosarcoma of the foot: A case report

Abstract

Extraskeletal osteosarcoma (ESOS) is a rare variant of osteosarcoma which occurs exclusively in the soft tissue without any bone involvement. Subcutaneous ESOS, in particular, is very rare and is seen in <10% of cases. Here, we report a case of a subcutaneous tumor in the fourth web space of the left foot in a 73-year-old man. The diagnosis of ESOS was made on histology and by immunohistochemical reactivity to special AT-rich sequence-binding protein 2 (SATB2), which is a sensitive, nuclear marker of osteoblastic differentiation. We present this case because of its rarity and the use of SATB2 immunohistochemistry to confirm the diagnosis.