Pseudomalignt osseous tumor of soft tissue is rare and benign disease. Fine and Stout(1956), described a benign soft tissue tumor exhibiting sarcoma-like features, so called “pseudomalignant osseous tumor of soft tissue”. Classification of the myositis ossificans was mentioned by Noble(1924) 1) myositis ossificans progressiva. 2) traumatic myositis ossificans circumscripta. 3) myositis ossificans circumpscripta without history of trauma. Jefferys and Stiles referred to this last condition as “pseudomalignat osseous tumor of soft tissue”. There was no history of trauma on seudomalignant osseous tumor of soft tissue, so this picture can be distinguished from myositis ossificans. The term of pseudomalignant is justified by the sacroma-like appearance of the soft central region as osteosarcoma. The “zone phenomenon” in this lesion described by Ackerman(1956); That is mature bone at the periphery and connective tissue at the center. This non-tumorous growth must be distinguished from osteogenic sarcoma, because it is benign, local excision is curative and has a good prognosis.