Cytarabine Crystals in CSF

Abstract

Distinguish the discordant microscopic observations between hemocytometer and Wright-stained concentrated CSF slide of patients with cytarabine crystals. The method incorporated in this study is a careful review of patient history and comparison of microscopic elements on the patient’s cerebrospinal fluid. CSF from a 16-year-old male. AML, FLT3 positive. A bone marrow aspirate, flow cytometry on bone marrow, and spinal tap were performed on the same day. The aspirate showed a hypocellular/hemodilute sample with trilineage hematopoiesis and 11% myeloblasts. Flow cytometry results included 21% atypical myeloid blasts and 44% atypical/immature monocytes. Eight fresh RBCs and 0 WBCs were observed on the hemacytometer. Eleven WBCs were noted on the cytospin slide; 100% were normal lymphocytes. Thirty-none variably sized, round cells (some with small inclusions) were seen on the hemacytometer but could not be recovered on the cytospin, despite using various stains. After much discussion with pathologists and microbiologists, it was discovered that the cells were cytarabine crystals. The patient had two recent doses of 50 mg cytarabine 2 weeks and 1 week prior to the lumbar puncture and bone marrow procedures. Cytarabine crystals can be an interfering microscopic examination that would show discordant results of cellular elements counted in hemocytometer vs concentrated Wright-stained smears.