A Rare Case of Systemic Mastocytosis with Associated Hematologic Neoplasm (SM-AHN) Involving Chronic Myeloid Leukemia: A Case Report and Literature Review.

BACKGROUND Single or multiple cell line dysplasia is a characteristic feature of myelodysplastic syndrome. However, significant dysgranulopoiesis is not a feature of chronic myeloid leukemia (CML). Systemic mastocytosis (SM) with an associated hematologic neoplasm (SM-AHN) comprises 5% to 40% of cases of SM. All types of hematologic neoplasms have been previously reported, although CML has been rarely encountered. CASE REPORT A 28-year-old male presented with a 3-month-history of weight loss and massive splenomegaly. Peripheral blood revealed marked leukocytosis, shift to left with 13% blasts. There was evident dysgranulopoiesis that raised a provisional diagnosis of myelodysplastic/myeloproliferative neoplasm. Bone marrow (BM) examination revealed granulocytic hyperplasia with 10% blasts and significant dysgranulopoiesis. Unexpectedly, cytogenetic analysis revealed t(9;22) with BCR/ABL1 rearrangement, diagnostic of chronic myeloid leukemia in an accelerated phase. The patient was started on dasatinib 100 mg upfront, however, he failed to respond, with increasing leukocytosis. Repeat BM examination showed persistence of the findings with 8% blasts. At this time, aggregates of mast cells with aberrant expression of CD25 were elicited, thus concluding the diagnosis of SM-AHN. The patient failed multiple lines of treatment (dasatinib, nilotinib, hydroxyurea, cytarabine subcutaneous, 6-mercaptopurine and interferon) and progressed to the blast phase a few months later. CONCLUSIONS We report an unusual case of CML, presented with significant dysgranulopoiesis with an aggressive clinical course including SM uncovered during the disease course with subsequent transformation to the blast phase. The different biological behavior of this case underscores the need for studies on a larger number of cases to explore the significance of the aforementioned coexistent features.