Chronic myeloid leukemia is a clonal expansion of hematopoietic progenitor cells characterized by exaggerated proliferation of granulocytic lineage, with chronic phase, accelerated phase and blast crisis. Accelerated phase and blast crisis may be associated with extramedulary disease. Extramedullary transformation of CML can be determined both in nodal and extranodal sites. Non-Hodgkin lymphoma is rare in chronic myeloid leukemia and may be misdiagnosed as an extramedullary lymphoid blast transformation; the majorities are T-cell lymphomas with an immature thymic phenotype, while peripheral B-cell lymphomas are rarer. We report the case of a 79-year-old woman carrier Ph+ chronic myeloid leukemia who developed at eight months of diagnosis an accelerated phase of CML associated simultaneous with a tumor of soft palate, which was initial considering an extramedullary disease. The patient was treated with specific chemotherapy for accelerated phase of CML (Cytosinarabinoside) + Anagrelide, and reversed to secondary chronic phase of CML, but soft palate tumor persists. The immunohistochemical findings of bone marrow trephine biopsy examination showed chronic phase of CML (negativity for immature cells such as CD34, Tdt) and the biopsy of soft palate tumor and immunohistochemical findings revealed a primitive non-Hodgkin lymphoma (NHL) with medium B-cells (CD20, CD79a positive) and excluding an extramedullary blast crisis (CD34 negative, Tdt negative). Cytogenetic analysis in tumor revealed absence of Philadelphia chromosome. The patient was treated with local radiotherapy for NHL, with a favorable evolution and Hydroxyurea 1 g/day for CML with hematological remission. A localized lymphoid neoplasm may be an extramedullary localized blast crisis of CML or a distinct malignancy, with distinguished therapy and prognosis. A correct diagnosis based on a complex investigation: immunohistochemistry, conventional cytogenetic analysis and fluorescence in situ hybridization (FISH), molecular analysis (Southern blot and RT-PCR) is necessary. Further studies are required to clarify the pathogenetic relationship between chronic myeloid leukemia and non-Hodgkin lymphomas.