Extramedullary Involvement by Chronic Myelogeneous Leukemia in Five Patients With Unusual Clinicopathologic Features: A Review of the Effectiveness of Tyrosine Kinase Inhibitors

Chronic myelogeneous leukemia (CML) is associated with BCR-ABL1 fusion gene leading to an abnormal tyrosine kinase molecule. The accepted first-line treatment is imatinib mesylate (IM). CML uncommonly occurs in the extramedullary sites at initial presentation or relapse. Here we report five adult patients with CML who developed myeloid sarcoma (MS) while on treatment with IM. A retrospective medical chart analysis was performed to identify CML patients with MS who were diagnosed and treated at the University of Alabama at Birmingham. The age ranged between 21 and 36 years (median: 28.5) with a male to female ratio of 4:1. All of the patients were diagnosed with CML in chronic phase with initial treatment including IM. The median interval period between the initial diagnosis of CML and MS was 27 months (range 7 - 60 months). The sites of extramedullary involvement included lymph nodes (n = 2), central nervous system (n = 2) and hepatobiliary organs (n = 1). All patients were treated with either induction therapy or stem cell transplant (SCT) following the diagnosis of MS. The median survival was 16 months (range 1 - 72 months). The longest survival was observed in a patient who successfully received SCT therapy. IM is frequently used as the first therapeutic choice in new diagnosed CML; however, its penetration and effectiveness in extramedullary tissue is still unclear. The current report also supports the literature with less favorable prognosis of CML in younger individuals.