Essential thrombocythemia

ICD-O-1 Morphology

9962/1: Idiopathic thrombocythemia
Effective 1978 - 1991

ICD-O-2 Morphology

9962/1: Idiopathic thrombocythemia
Effective 1992 - 2000

ICD-O-3 Morphology

9962/3: Essential thrombocythemia
Effective 2001 and later


for cases diagnosed 2001 and later

Primary Site(s)

Primary site must be bone marrow (C421). Blood and bone marrow are the primary sites of involvement.

Abstractor Notes

Neoplasm is usually suspected when the patient has a CBC or peripheral blood smear that shows an overproduction of platelets. More than half of the patients are asymptomatic at the time of diagnosis.

A diagnosis of "post essential thrombocythemia myelofibrosis" is a progression of essential thrombocythemia and would be the same primary.

50-60% of patients will have a positive JAK2.

Aspirin, in low dose only (< 100 mg/day) is used as treatment for this disease.

For more information, see the NCI website:

Diagnostic Confirmation

This histology can be determined by positive histology (including peripheral blood) with or without genetics and/or immunophenotyping. Review the Definitive Diagnostic Methods, Immunophenotyping and Genetics Data sections below, and the instructions in the Hematopoietic Manual for further guidance on assigning Diagnostic confirmation.


Not Applicable

Module Rule


Alternate Names

Early essential thrombocythemia
Essential hemorrhagic thrombocythemia
Essential thrombocytosis
Hemorrhagic thrombocythemia
Idiopathic hemorrhagic thrombocythemia
Idiopathic thrombocythemia
Idiopathic thrombocytosis
Primary thrombocythemia
Primary thrombocytosis
Thrombocythemia vera


Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm (MPN) that primarily involves the megakaryocytic lineage. It is characterized by sustained thrombocytosis in the peripheral blood and increased numbers of large, mature megakaryocytes in the bone marrow and clinically by the occurrence of thrombocytosis and/or hemorrhage.

Because there is no known genetic or biological marker specific for ET, other causes of thrombocytosis must be excluded, including other MPNs, inflammatory and infectious disorders, hemorrhage, and other types of hematopoietic and non-hematopoietic neoplasms.

The presence of BCR-ALB1 gene fusion excludes the diagnosis of ET.

The diagnostic criteria for ET are:
Major criteria
1. Platelet count greater than or equal to 450 x 10(3)/L
2. BM biopsy showing proliferation mainly of the megakaryocyte lineage with increased numbers of enlarged, mature megakaryocytes with hyperlobulated nuclei. No
significant increase or left shift in neutrophil granulopoiesis or erythropoiesis and very rarely minor (grade 1) increase in reticulin fibers
3. Not meeting WHO criteria for BCR-ABL11 CML, PV, PMF, myelodysplastic syndromes, or other myeloid neoplasms
4. Presence of JAK2, CALR, or MPL mutation

Minor criterion
Presence of a clonal marker or absence of evidence for reactive thrombocytosis

Diagnosis of ET requires meeting all 4 major criteria or the first 3 major criteria and the minor criterion

Definitive Diagnostic Methods

Bone marrow biopsy
Clinical diagnosis
Genetic testing

Genetics Data

CALR (~30% of cases)
JAK2 V617F (~50% - 60% of cases)
MPL (~12% of cases)




Other therapy

Transformations from


Corresponding ICD-9 Codes

238.71 Essential thrombocythemia

Corresponding ICD-10 Codes

D47.3 Essential (hemorrhagic) thrombocythemia

Corresponding ICD-10-CM Codes (U.S. only)

D47.3 Essential (hemorrhagic) thrombocythemia (effective October 01, 2015)

Signs and Symptoms

Bleeding from mucosal surfaces
Burning or tingling in the hands or feet
GI bleeding
Redness and warmth of the hands or feet
Vision or hearing problems

Diagnostic Exams

Blood chemistry studies
Cytogenetic analysis
JAK 2 gene mutation test
Peripheral blood smear

Progression and Transformation


Epidemiology and Mortality

Age: 50-60 years median age
Incidence: 0.6-2.5 per 100, 000 cases per year
Sex: no male or female predominance
Survival: 10-15 years median survival


Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition)
IARC: Lyon 2017
Section: Myeloproliferative neoplasms
Pages: 50-53

International Classification of Diseases for Oncology, Third Edition, Second Revision. Geneva: World Health Organization, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes

National Cancer Institute
Section: General Information About Myeloproliferative Neoplasms