A 56-year-old man had a history of acute promyelocytic leukemia and had been in remission for 2 years. He developed the new onset of seizures. Brain MRI showed 2 well-circumscribed right parietal lobe lesions (one lesion shown above). Spinal fluid cytology was negative for malignant cells. Bone marrow aspiration and biopsy were negative. The neurosurgeon resected these lesions that were within brain tissue and distinct from the meninges. Microscopic review revealed an infiltrate of immature cells, CD10- and CD117-positive, and containing granules that appeared as promyelocytes.

Granulocytic sarcomas are rare collections of acute leukemic cells that can occur in any soft tissue area, including bone, skin, lymph nodes, breast, ovary, meninges, orbit, and optic nerve. In early reports, they were known as chloromas, because of their rich myeloperoxidase content that appeared green. Granulocytic sarcomas appear in individuals who have normal marrows. They usually precede marrow involvement by acute leukemia or chronic myelogenous leukemia by months to years.

After the neurosurgical procedure, the patient received localized CNS radiation. Three months later, a repeat bone marrow aspiration showed near-total replacement with promyelocytes. He was given aggressive chemotherapy followed by consolidation with all-trans retinoic acid and arsenic trioxide. Four months later, there was no evidence of recurrence, either on MRI or in the marrow.