A patient presents with a platelet count of 700 x I0VL with abnormalities in size, shape and granularity of platelets. He has a WBC count of 12 x 107L, hemoglobin of 11g/dl and there is absence of the Philadelphia chromosome. What is the MOST likely diagnosis?

Laboratory results in this patient shows elevated abnormal platelets along with slightly elevated WBC and normal hemoglobin. All of these indicates a diagnosis of essential thrombocythemia. Blood film examination in these patients usually shows large platelets that may stain poorly. Essential thrombocythemia is a myeloproliferative neoplasm, it is a clonal hematopoietic stem cell disorder characterized by an isolated thrombocytosis and associated with thrombotic and hemorrhagic complications. it is associated with mutation in JAK2 or MPL. Bone marrow aspiration and trephine biopsy is paicularly recommended in suspected cases of ET that are negative for mutations in JAK2 and MPL. Ref: Williams Hematology, 8e chapter 87 by Philip A. Beer; Anthony R. Green.