Epithelioid inflammatory myofibroblastic sarcoma arising in the maxilla: first reported case in the jaws.

Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is a rare variant of inflammatory myofibroblastic tumors located mostly in the intra-abdominal region. Herein, we present a case of a 32-year-old male with a lobulated growth in the right maxilla. Radiology revealed a solitary osteolytic lesion with an irregular margin, causing buccal and palatal cortex erosion. Histopathology revealed a tumor composed of spindle-shaped fascicles that blend into sheets of round to ovoid-shaped epithelioid cells, areas of myxoid changes, and necrosis. Tumor cells showed a moderate amount of eosinophilic cytoplasm, large vesicular nuclei with coarse chromatin, nuclear pleomorphism, and increased mitoses. Tumor cells were immunopositive for ALK-1, focal positivity for smooth muscle actin, panCK, epithelial membrane antigen, and immunonegativity for CD 30, desmin, CD34, and STAT6. P53 showed a wild-type staining pattern, and INI-1 expression was retained. The Ki-67 proliferative index was 22%. To the best of our knowledge, this is the first case of EIMS occurring in the maxilla.