The WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues

Essential Thrombocythemia

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Syed A. Abutalib, MD

Syed A. Abutalib, MD

L. Jeffrey Medeiros, MD

L. Jeffrey Medeiros, MD

The ASCO Post is pleased to present Hematology Expert Review, an ongoing feature that quizzes readers on issues in hematology. In this installment, Drs. Abutalib and Medeiros explore the recently updated World Health Organization (WHO) classification of hematopoietic and lymphoid tissue malignancies, focusing on essential thrombocythemia. For each quiz question that follows, select the one best answer. The correct answers and accompanying discussions appear below. 

Question 1 

Which of the following is one of the four major criteria for the diagnosis of essential thrombocythemia? 

A. Platelet count ≥ 450 × 109 /L 

B. Absence of reactive thrombocytosis 

C. Presence of a clonal marker other than mutation of JAK2, CALR, or MPL 


Dr. Abutalib is Assistant Director, Hematology and Hematopoietic Cell Transplantation Director, Hematopoietic Cell Transplant Apheresis Service, Cancer Treatment Centers of America, Zion, Illinois, Editor-in-Chief, Advances in Cell & Gene Therapy. Dr. Medeiros is Professor and Chair, Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston.

Question 2 

Approximately what percentage of essential thrombocythemia cases are triple-negative for JAK2, CALR, or MPL mutations? 

A. 12% 

B. 60% 

C. 30% 

Question 3 

Which major peripheral blood smear abnormality is generally seen in essential thrombocythemia? 

A. Leukoerythroblastosis 

B. Marked thrombocytosis 

C. Teardrop-shaped red blood cells 

Question 4 

Which bone marrow abnormality is commonly observed in essential thrombocythemia?

A. Marked proliferation of megakaryocytes in clusters 

B. Marked proliferation of bizarre, highly atypical megakaryocytes 

C. Marked proliferation of megakaryocytes dispersed throughout the bone marrow 

Question 5 

Which of the following statements about bone marrow findings in essential thrombocythemia is correct? 

A. The finding of significant reticulin fibrosis or any collagen fibrosis at presentation includes the diagnosis of essential thrombocythemia. 

B. The small megakaryocytes with hypersegmented nuclei seen in essential thrombocythemia contrast with the very large nonlobated megakaryocytes seen in myelodysplastic syndrome with isolated del(5q). 

C. The finding of combined granulocytic and erythroid proliferation is uncommon. ■

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Answers to Hematology Expert Review Questions

Question 1 

Which of the following is one of the four major criteria for the diagnosis of essential thrombocythemia? 

Correct Answer: A. Platelet count ≥ 450 × 109/L. 

Expert Perspective 

The diagnosis of essential thrombocythemia requires that all four major criteria or the first three major...