Granular acute lymphoblastic leukemia: a case report and literature review.

Authors report a rare case of granular acute lymphoblastic leukemia (ALL) in a 45-year-old woman with a history of multiple myeloma. The patient's lymphoblasts contained large numbers of distinctive cytoplasmic granules closely mimicking heavily granulated myeloblasts in acute myeloid leukemia. These blasts were completely negative for myeloperoxidase but positive for acid phosphatase and Periodic Acid-Schiff reaction by cytochemical staining. Immunophenotype analysis by immunohistochemistry clearly demonstrated precursor B-cell phenotype. Granular ALL occurs approximately 2 to 7% in childhood populations but is extremely rare in adults. Such cases may cause problematic distinction from myeloid differentiation and lead to misdiagnosis of acute myeloid leukemia. Ten cases of adult granular acute lymphoblastic leukemia described to date in the literature were also reviewed.