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Year : 2011  |  Volume : 54  |  Issue : 1  |  Page : 117-120
JAK2-positive Philadelphia-negative myeloproliferative neoplasms


Department of Pathology, Dr. Ram Manohar Lohia Hospital, PGIMER, New Delhi, India

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Date of Web Publication7-Mar-2011
 

   Abstract 

The recent discovery of the JAK2 mutations has rekindled interest in the approach to classic BCR/ABL-negative myeloproliferative neoplasms (MPNs) in terms of both diagnostic evaluation and treatment. However, additional clinical, laboratory and histological parameters play a key role to allow diagnosis and subclassification, regardless of whether JAK2 V617F mutation is present or not. Here are two cases which incidentally presented with splenomegaly and moderate leukocytosis, and were diagnosed as MPN-primary myelofibrosis (PMF) in prefibrotic phase and polycythemia vera (PV), respectively, using revised World Health Organization (WHO) 2008 criteria.

Keywords: JAK2-positive, leukocytosis, Philadelphia-negative MPN, primary myelofibrosis

How to cite this article:
Sharma A, Buxi G, Marwah S, Yadav R. JAK2-positive Philadelphia-negative myeloproliferative neoplasms. Indian J Pathol Microbiol 2011;54:117-20

How to cite this URL:
Sharma A, Buxi G, Marwah S, Yadav R. JAK2-positive Philadelphia-negative myeloproliferative neoplasms. Indian J Pathol Microbiol [serial online] 2011 [cited 2019 Nov 17];54:117-20. Available from: http://www.ijpmonline.org/text.asp?2011/54/1/117/77355



   Introduction Top


For many years, the diagnosis of BCR/ABL-negative chronic myeloproliferative disorder (CMPD) was mainly based on clinical symptoms, cytomorphology and histomorphological findings. [1] The recent discovery of the JAK2 mutations has rekindled interest in the approach to classic BCR/ABL-negative myeloproliferative neoplasms (MPNs) in terms of both diagnostic evaluation and treatment. [2]

Here are two case reports which incidentally presented with splenomegaly and mild to moderate leukocytosis, and were diagnosed as MPN-primary myelofibrosis (PMF) and polycythemia vera (PV), respectively, using revised World Health Organization (WHO) 2008 criteria. [2]

Case 1

A 48-year-old female, known and followed up case of type 2 diabetes mellitus for past 16 years, complained of fullness in left flank region, pruritic furuncles over neck and chest region and weakness for 2 weeks. There was no past history of hypertension or tuberculosis.

On general examination, the patient was conscious, oriented with stable vitals. Her chest, cardiovascular, central nervous system examination was within normal limits. Per abdomen examination showed enlarged liver, up to 8 cm below costal margin, and 12 cm splenic enlargement. No free fluid was present in the abdominal cavity.

Her chest X-ray was normal. Liver function test, kidney function test, serum proteins, lipid profile, iron profile, serum vitamin B12 and folic acid were all within normal limits. Serum β2-microglobulin and lactate dehydrogenase (LDH) were markedly elevated.

Hemogram showed normocytic, normochromic picture with neutrophilic leukocytosis [total leukocyte count (TLC): 28,000 cells/mm 3 and polymorphs: 82%] and adequate platelets. No immature cells were seen, including normoblasts. There was no basophilia or eosinophilia. Tear drop cells were not seen. Her neutrophil alkaline phosphatase (NAP) score was 158 (control: 35-100). Thus, impression of neutrophilia was given and the patient was asked to be on hematological follow-up.

Hematological follow-up showed persistent neutrophilic leukocytosis. Bone marrow (BM) aspirate was done which was diluted and a BM biopsy was advised.

BM biopsy was hypercellular for her age, showing disturbed topography. There was an increase in the number of neutrophils and atypical megakaryocytes. Erythroid series of cells showed normal maturation. Myeloid series of cells were seen in different stages of maturation with no increase in myeloblasts. Megakaryocytes were increased in number, seen in clusters at places. Some of them showed features of dysmegakaryopoiesis [Figure 1]. No granuloma or hemoparasite was seen. No evidence of fibrosis was seen.
Figure 1: BM biopsy: (a) Cellular for age showing disturbed topography (H and E, ×10); (b)megakaryocytes are increased in number, seen in clusters at places, some of them showing the features of dysmegakaryopoiesis (H and E, ×40)

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In view of the above clinical features, hemogram, high NAP score and BM biopsy features, a possibility of MPN was suggested.

Molecular studies for BCR/ABL translocation were negative. Molecular genetic analysis for JAK2 mutation was found positive for V617F mutation in exon 14 in JAK2 gene.

A final diagnosis of Philadelphia-negative JAK2-positive PMF was given. Though there was no fibrosis, it was a case of prefibrotic stage of PMF fulfilling all the revised 2008 WHO criteria. All the secondary causes of myelofibrosis were ruled out.

Patient responded to the conventional therapy of hydrea and anagrelide as there was more than 50% reduction in TLCs and regression of spleen within a span of 2 months and she is still under follow-up.

Case 2

A 59-year-old male, known and followed up case of hypertension and coronary artery disease, was admitted with complaints of frequent attacks of dizziness and headache for 2 weeks.

On general examination, the patient was conscious, oriented with stable vitals. His chest, cardiovascular, central nervous system examination was within normal limits. Abdominal examination revealed a 12-cm enlarged spleen. No free fluid was present in the abdominal cavity.

The patient was admitted in cardiology unit for cardioarteriogram (CAG), but CAG could not be done due to persistent leukocytosis and thrombocytosis. Blood investigations revealed normocytic, normochromic picture (hemoglobin: 17.6 g%), TLC of 33,900 cells/mm 3 (polymorphs: 91%) and thrombocytosis (platelet count: 6.33 lakhs/mm 3 ). No immature cells or tear drop cells were seen in the peripheral smear. There was no basophilia or eosinophilia. The patient was referred to general medicine.

His chest X-ray was normal. Liver function test, kidney function test, serum proteins, lipid profile, iron profile, serum vitamin B12 and folic acid, serum immunoelectrophoresis, serology for kalazar were all within normal limits. Magnetic resonance imaging of brain revealed age-related cerebral atrophy and arteriosclerosis changes. EEG showed normal study. Serum LDH was markedly elevated. The patient was managed with all symptomatic and supportive management.

His regular hematological follow-up showed persistent neutophilic leukocytosis with thrombocytosis. He had consistent Hb more than 17 g% with hematocrit of 56%. Serum erythropoietin was markedly reduced. NAP score was 280 (control: 35-100). Bone marrow aspirate smears were markedly cellular with myeloid to erythroid ratio of 1.5-2:1. Myeloid and erythroid series of cells showed normal maturation. Megakaryocytes were abundant, showed anisocytosis and were functioning. At places, they were seen in clusters and few showed dysplastic features. No hemoparasite or granuloma was seen.

BM biopsy showed bony trabeculae enclosing marrow spaces which were hypercellular for his age. Topography of the marrow was disturbed and showed the same features as seen in the aspirate [Figure 2]a, b. In addition, there was fibrosis in the marrow, infiltrating into marrow spaces (reticulin grade 3-4) [Figure 2]c, d.
Figure 2: BM biopsy (a) showing bony trabeculae enclosing marrow spaces which are hypercellular for age (H and E, ×40); (b) abundant functioning megakaryocytes of varying sizes are seen. At places, they are seen in clusters and few show dysplastic features (deeply lobulated nuclei) (H and E, ×100); (c) thick coarse fiber network (grade 3-4) (reticulin stain, ×40); (d) coarse collagen fibers (Masson Trichome stain, ×40)

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In view of the above clinical features, hemogram, high NAP score, increased hematocrit, decreased erythropoietin levels and BM biopsy picture, a diagnosis of MPN-PV was given.

Molecular studies for BCR/ABL translocation by reverse transcriptase-polymerase chain reaction (RT-PCR) were negative. Molecular genetic analysis for JAK2 mutation was found positive for V617F mutation in exon 14 in JAK2 gene.

Based on molecular studies, a final diagnosis of Philadelphia-negative JAK2-positive MPN-PV was given.

Patient responded to the conventional therapy of hydrea and anagrelide as there was more than 60% reduction in TLCs, decrease in the Hb and hematocrit values and platelet count. Also, there was regression of spleen and reduction in the frequency of syncopal attacks within 45 days of treatment and he is still under follow-up.


   Discussion Top


The 2008 WHO classification system for hematological malignancies is comprehensive and includes histology and genetic information. This revised document continues to promote the recognition of histologic categories as a necessary first step toward the genetic characterization of myeloid malignancies. [2]

The previously used term CMPD is replaced by MPN. [3] MPN includes chronic myeloid leukemia-BCRABL positive, chronic neutrophilic leukemia, PV, PMF, essential thrombocythemia (ET), chronic eosinophilic leukemia (CEL), mastocytosis and MPN (unclassifiable). Presently, the most commonly recognized mutation in BCRABL-negative MPN is JAK2 V617F. [3]

The diagnostic criteria for PV/ET and PMF were revised by incorporating recently described molecular markers (JAK2 and MPL mutations) as well as underscoring the role of histology in differentiating reactive from clonal myeloproliferation.

Both the above cases fulfilled the revised WHO 2008 criteria for PMF and PV, respectively, as depicted in [Table 1]. [1]
Table 1: The 2008 WHO diagnostic criteria for idiopathic myelofibrosis and PV as seen in the two cases

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The association of these above major and minor criteria, along with clinical history of hypertension and MI, raised hematocrit and splenomegaly in the Case 2 gave confirmed diagnosis of MPN secondary to PV.

At times, initial PV with thrombocytosis may mimic ET on histology. [4] Some patients with ET may also develop PV. Sometimes, patients with PMF are indistinguishable from patients developing myelofibrosis during the course of PV, especially when there is no history of phlebotomy. [5]

Recently, some authorities have raised concern regarding the inclusion of histologic features as diagnostic parameters for PV, ET and PMF. [3] In particular, the histologic distinction between prefibrotic stage of PMF (a stage often associated with marked thrombocytosis in peripheral blood and granulocytic and atypical megakaryocytic proliferation with minimal, if any, fibrosis in the bone marrow) and ET has been questioned.

ET is characterized by clusters of enlarged mature megakaryocytes close to sinusoids, whereas erythropoiesis and granulopoiesis are normal. However, PMF is characterized by marked hypercellularity, left shifted increased granulopoiesis and a particular megakaryocyte morphology with atypical nuclear features. [2]

BM in PV shows prominence of megakaryocytes, clustered around marrow sinusoids or lying close to bony trabeculae, and may show pleomorphism. They have deeply lobulated nuclei and lack bizarre dysplastic features as seen in Case 2 [Figure 2]. [6]

JAK2 postivity can be seen in all PV patients and in half of those with ET and PMF. [5] Therefore, JAK2 V617F is not specific for any single MPN, nor does its absence exclude any MPN. [3]

Recent studies on the JAK2 mutational burden have proposed the concept of a biological continuum from JAK2-positive ET to JAK2-positive PMF. This is supported by the fact that there are no differences between prefibrotic PMF and true ET, either clinically, biochemically or with regard to JAK2 status, thrombohemorrhagic complications, survival or myelofibrotic transformation. [5] Some authors are of the opinion that myelofibrosis with myeloid metaplasia (MMM) is the advanced stage of an untreated disseminated hematological cancer which accordingly should be treated upfront when the disease presents in the very early stage as PV or ET, when the cancer stem cells have still not regressed from the bone marrow.("carcinoma in situ"). [5]

The findings of generalized pruritic skin lesions in Case 1 and recurrent seizure attacks in Case 2 may be supported by a recent report. It proposes that JAK2 postivity may be associated with increased leukocyte counts, history of thrombosis or pruritis and a less frequent need for blood transfusion. [5] Besides, Ishii et al. [7] have also stated that pruritis is a common symptom in Ph-negative CMPD, occurring in approximately 50% of patients. Though its pathophysiology is unclear, they demonstrated that mast cells play a pivotal role in the pathogenesis of myeloproliferative disorders. [7]

Normalization of elevated blood cell counts in the early phase of CMPDs, ET and PV should be the therapeutic target in the future using α-interferon as monotherapy or in combination with conventional (hydroxyl urea and anagrelide) and JAK2 inhibitors. [5] Therapy is aimed at causing the reduction in risk of thrombohemorrhagic complications and ultimately the development of severe bone marrow failure and myeloid metaplasia. Both our cases responded well to the conventional therapy. [5]


   Conclusion Top


In an elderly patient presenting with incidental splenomegaly and minimal to borderline leukocytosis, diagnosis of MPN should always be considered. In the recent WHO classification, diagnostic algorithms for PV, ET and PMF have substantially changed to include information regarding JAK2 V617F mutation. However, additional clinical, laboratory and histologic parameters play key role to allow diagnosis and subclassification, regardless of whether JAK2 V617F mutation is or is not present.

 
   References Top

1.Tefferi A, Thiele J, Vardiman JW. The 2008 World Health organization classification system for myeloproliferative neoplasms: Order out of chaos. Cancer 2009;115:3842-7.  Back to cited text no. 1
[PUBMED]  [FULLTEXT]  
2.Haferlach T, Bacher U, Kern W, Schnittger S, Haferlach C. The diagnosis of BCR/ABL- negative Chronic myeloproliferative diseases(CMPD): A comprehensive approach based on morphology, cytogenetics and molecular markers. Ann Hematol 2008;87:1-10.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Vardiman JW, Thiele J, Arber DA, Brunning RD, Borowitz MJ, Porwit A, et al. The 2008 revision of the WHO classification of myeloid neoplasms and acute leukemia: Rationale and important changes. Blood 2009;114:937-51.   Back to cited text no. 3
[PUBMED]  [FULLTEXT]  
4.Thiele J, Kvasnicka HM, Diehl V. Initial (latent) polycythemia vera with thrombocytosis mimicking essential thrombocythemia. Acta haematol 2005;113:213-9.  Back to cited text no. 4
    
5.Hasselbalch HC. Myelofibrosis with myeloid metaplasia: The advanced phase of an untreated disseminated hematological cancer. Time to change our therapeutic attitude with early upfront treatment? Leuk Res 2009;33:11-8.  Back to cited text no. 5
[PUBMED]  [FULLTEXT]  
6.Thiele J, Kvasnicka HM, Orazi A, Tefferi A, Birgegard G. Polycythaemia vera. In: Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al. editors. Pathology and genetics of tumors of hematopoietic and lymphoid tissues, 4 th ed. Lyons,France: IARC Press; 2008. p. 40-3.  Back to cited text no. 6
    
7.Ishii T, Wang J, Zhang W, Mascarenhas J, Hoffman R, Dai Y, et al. Pivotal role of mast cells in pruritogenesis in patients with myeloproliferative disorders. Blood 2009;113:5942-50.  Back to cited text no. 7
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Correspondence Address:
Anjali Sharma
Department of Pathology, Dr. Ram Manohar Lohia Hospital, PGIMER, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.77355

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