Mediastinal granulocytic sarcoma

Granulocytic sarcoma is an unusual variant of myeloid malignancy in which there is an extramedullary tumor mass composed of myeloblasts or myeloblasts and more mature neutrophils. It rarely occurs in mediastinum and clinically may resemble a mediastinal lymphoma. We report a patient who was initially diagnosed as malignant lymphoma based on the previous biopsy specimen. The diagnosis of granulocytic sarcoma is not difficult with careful histopathologic evaluation and immunohistochemical staining.