Extramedullary B lymphoblastic crisis of CML, presenting as a leptomeningeal tumor - A case report

We report here on a rare case of a patient who presented with an extramedullary B lymphoblastic crisis as an initial manifestation of chronic myelogenous leukemia (CML). A 71-year-old man visited the emergency room due to suddenly developed dysarthria and right side weakness. Emergency craniotomy was done under the presumptive diagnosis of subdural hemorrhage. During the operation, a poorly demarcated firm mass was identified in the leptomeningeal space. Microscopically, the majority of the tumor was composed of monotonous immature cells with blast morphology, and these cells were immunoreactive for TdT, CD34, CD10 and CD20, indicating the precursor B-cell phenotype. The peripheral area of the tumor consisted of myeloid cells in various stages of maturation, and these cells were reactive for myeloperoxidase, chloroacetate esterase, CD43 and CD15. FISH analysis using the LSI bcr-abl dual color probe showed gene fusion signals in both the B-lymphoblasts and myeloid cells. The peripheral blood and bone marrow findings were consistent with CML with no evidence of a blast crisis. Cytogenetic study of the bone marrow demonstrated the 46, XY, t(9;22)(q34;q11) chromosome. A diagnosis of extramedullary B lymphoblastic blast crisis in a patient with Philadelphia chromosome-positive CML was made. Despite treatment, the patient died 3 months after he was diagnosed.