MRI of perineural extramedullary granulocytic sarcoma.

Granulocytic sarcoma is an extramedullary solid tumour consisting of myelogenous leukaemic blast cells, usually seen in acute myeloid leukaemia and less commonly in patients with chronic myeloid leukaemia or myeloproliferative disorders. Blast cells have a predilection for periosteal and perineural regions and rarely precede evidence of systemic disease. We present two patients, aleukaemic on peripheral blood counts, both at presentation and during subsequent treatment. We present the MRI features of this rare but important condition.