RESUMO
BACKGROUND: Chronic myelogenous leukemia (CML) is a chronic myeloproliferative disease characterized by a massive overproduction of myeloid cells. It is associated with the Philadelphia chromosome [Ph1, t (9; 22) (q34; q11)] or BCR-ABL fusion gene. CML usually undergoes a triphasic clinical course ending in a blast crisis, an accelerated phase of blasts and promyelocyte production. Ten percent of CML patients reach the blast crisis phase, with 20-30% of leukemias belonging to B-cell lymphoid lineage. However, a transformation of CML into T-cell acute lymphoblastic leukemia (T-ALL) is rare. CASE PRESENTATION: We present a 56-year-old male patient, known case of hypertension and Ph1 CML of eight years with a family history of Gaucher disease who developed T-ALL. The patient presented with lymphadenopathy and severe anemia, needing packed RBC transfusion, neutropenia and thrombocytopenia at the admission. However, the monocytes and basophils percentage were high. The patient underwent a cervical lymph node core biopsy, and the immunohistochemistry stains showed an invasion of neoplastic cells positive for CD3, CD5, BCL2, CD34, TdT and focally positive for C-Kit and negative for CD20, CD56 and pan-CK. These histopathology features were consistent with T-cell acute lymphoblastic leukemia (T-ALL). CONCLUSION: Blast crisis remain a challenge in CML management. It's of great importance to do a full proper workup including lymph nodes biopsies. The aim is to reverse blast crisis and restore the chronic phase.