Precursor Lymphoblastic Lymphoma in the Extramedullary Tissue: A Rare Manifestation of Chronic Myeloid Leukemia in Blast Crisis.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by immature granulocytes in peripheral blood and bone marrow. In 95% of cases, it is always due to the presence of Philadelphia chromosome characterized by the presence of reciprocal translocation between chromosome 9 and 22. However, in 7% -17% of individuals, extramedullary proliferation also occurs, either in skin, lymph nodes, bone or central nervous system (CNS), which could be either myeloid, lymphoid or mixed progenitor in origin. The present case is of a 23-year-old male who presented with lower limb weakness, bowel and urinary incontinence. His complete blood count (CBC) findings showed a raised white blood count (WBC) of 408 X 10E9/L. Peripheral film, bone marrow biopsy and immunohistochemistry showed findings consistent with CML in chronic phase. Bone marrow cytogenetic revealed the presence of Philadelphia chromosome. Simultaneously, magnetic resonance imaging (MRI) was done which revealed extradural mass at L1-L3 level; histopathological and immunohistochemistry findings showed features compatible with precursor B cell lymphoblastic lymphoma. His cerebrospinal fluid (CSF) cytology revealed similar blast cells. This extramedullary presence of lymphoid blast cells in the CNS put the patient in the rare entity of CML in blast crisis. He was started on tablet nilotinib and also received multiple cycles of intrathecal chemotherapy with cytosar, methotrexate and hydrocortisone. He also underwent radiotherapy of extradural mass. His lower limb weakness improved dramatically. However, after receiving the fourth cycle of intrathecal therapy, the patient died consequent to neutropenic sepsis. Extramedullary blast crisis in CML has a poor prognosis. Any patient with CML, presenting with CNS symptoms or lymph node enlargement should be thoroughly investigated for extramedullary blast crisis, as there is a considerable change in management and prognosis from the prototype CML in chronic phase.