Granulocytic sarcoma (chloroma). Presentation of an unusual case.

An unusual case of granulocytic sarcoma with a large retro-orbital tumor mass is described. The tumor had an uncommon cytomorphology and ultrastructure that mimicked a signet ring cell lymphoma. It was negative by chloroacetate esterase (CAE) stain. The patient was treated successfully with CHOP-regimen polychemotherapy and irradiation. Seventeen months after the initial diagnosis of malignant lymphoma, acute myeloid leukemia developed. Additional immunohistochemistry, including an immunoperoxidase staining for lysozyme, clearly demonstrated the early myeloid nature of the original tumor. This case emphasizes the importance of staining for lysozyme and other myeloid markers in addition to CAE staining in cases that demonstrate unusual morphological features.