Granulocytic sarcoma.

Granulocytic sarcoma (in the past sometimes called chloroma because of the grossly greenish tinge of the tumoral tissue due to the presence of the enzyme myeloperoxidase) is a dramatic manifestation of acute myelogenous or myelomonocytic leukemia. A soft-tissue or an organ mass created by leukemic cells dominates the clinical presentation or develops later in the course of the disease after an unsuccessful attempt at therapy. Sites of involvement include the skin, bones, sinuses, and orbits, but rarely the CNS or the interior of the globe. This issue of AJNR has two reports on the MR aspects of this disorder: one (1] describes four cases with orbital involvement, and the other (2] describes two cases involving either the sphenoidal sinus or the paraspinal region. All of the lesions in both reports showed the MR characteristics of hypointensity on T1-weighted images and isointensity or intermediate signal intensity on T2-weighted images. The two nonorbital cases [2] developed in adults on relapse of an already diagnosed and treated leukemia. Therefore these characteristics are of value for ruling out other neoplasms, which, with regard to paraspinal tumors, include neural neoplasms such as schwannoma or neurofibroma that are hyperintense on T2-weighted images. The report (1] on the four orbital cases portrays a quite different clinical picture: none of the affected children was known to have leukemia. Ocular adnexal granulocytic sarcomas, as described by Zimmerman and Font (3] in a series of 33 patients, most typically present without a diagnosed systemic leukemic disease and pose a particularly challenging subset of cases. Therefore, my remaining comments about granulocytic sarcoma are devoted to ocular adnexal cases. 263