PB1961 THREE CHRONIC MYELOID LEUKEMIA CASES THAT PRESENTED LIKE ESSENTIAL THROMBOCYTHEMIA
Authors: V. Aslan, U. Iltar, I. Nizam Ozen, M. Göçer, M. Çelik, E. Kurtoğlu, Ö. Erkal
Journal: HemaSphere (2019)

Background: 2016 WHO classification divides myeloprolipherative neoplasms into bcr‐abl positive and bcr‐abl negative neoplasms, not only because of treatment difference also because of the heterogeneity of clinical presentations in Chronic Myeloid Leukemia (CML) patients. Classical CML patients present very high leukocyte count with or without thrombocytosis and splenomegaly. In literature there are few CML cases that have first presentations as Essential Thrombocythemia (ET) with not remarkable leukocytosis. Aims: We report three CML cases presented as classical ET. Methods: 54 years old female patient referred to our hematology clinic because of very high platelet count. Platelet count was 2,578,000/mm 3 and WBC count was 15,800/mm 3 . She had no clinical history of thrombosis and no splenomegaly. After bone marrow biopsy we started hydroxyurea 2000 mg/day. After 20 days platelet count was still higher than 2,000,000/mm 3 . PCR results of JAK‐2 was negative but bcr‐abl IS‐PCR was positive so we started imatinib 400 mg/day. After 10 days of imatinib, platelet count decreased to 1.400,000/mm 3 and after one month of the imatinib treatment platelet count decreased to normal levels. The patient had no thrombosis during this period. After three months her PCR‐IS level decreased to 0,16%. Second case is 25 years old female patient that is referred from internal medicine because of high platelet count (678,000/mm 3 ). Her WBC count was normal and JAK‐2 mutation test was negative, so we searched for CALR and MPL mutations for Essential Thrombocytosis and results were negative. Proceeding from the experience of former patient, although there was no leukocytosis, we tested bcr‐abl with PCR‐IS and result was positive. After bone marrow biopsy we started imatinib 400 mg per day. In cytogenetic analysis Philadelphia chromosome was positive. One month later platelet count decreased to normal level. Minimal leukopenia observed. After three months PCR‐IS value decreased to 0.45%. Third patient is 40‐year‐old female patient that is referred our clinic with high platelet count (747,000/mm 3 ) WBC count was 8,800/mm 3 and JAK‐2 mutation was negative. Although her WBC count was normal we tested bcr‐abl with IS‐PCR and result was 12% positive. After bone marrow biopsy we started imatinib 400 mg/day. After 20 days her platelet count decreased to normal level. After three months IS‐PCR result was 0.14%. Results: Here we discussed three CML patients with marked thrombocytosis without remarkable leukocytosis. All three female patients had similar clinical findings. All patients had no splenomegaly, had no thrombosis event. They all had minimal basophilia at presentation (1600/mm 3 , 600/mm 3 , 600/mm 3 ) that was underestimated because in peripheral smears findings were normal. They all had very good response to imatinib treatment. Summary/Conclusion: CML patients that presents as ET are supposed to be rare but all three patients came to our center at dates between June and August 2018. Two of them had diagnosis of CML because of the experience from first patient. WHO classifications need bcr‐abl negativity for diagnosis of ET. With experience of these three patients we suggest to test all ET patients about bcr‐abl. Even tough normal WBC count and normal peripheral smear findings, absolute basophile count must be reconsidered.