Myelofibrosis is characterized by (typically) increased reticulin fibrosis or (less commonly) collagen fibrosis (trichrome stain). Hematologic malignancies are often leading culprits, but consideration of other etiologies should be considered.
The following categories and entities should be considered with the finding of myelofibrosis.
Diffuse increase of reticulin fibers with increased density and numerous intersections. Increased thick bundles of fibers consistent with collagen fibrosis. Osteosclerosis usually present.
In cases of MF2 or MF3, it is recommended to perform trichrome stain to evaluate for collagen fibrosis.
References
Marcellino B, Jamal El SM, Mascarenhas JO. Distinguishing autoimmune myelofibrosis from primary myelofibrosis. Clin Adv Hematol Oncol. 2018;16: 619–626.
Diffuse increase of reticulin fibers with increased density and numerous intersections. Increased thick bundles of fibers consistent with collagen fibrosis. Osteosclerosis usually present.
Photomicrographs
References
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
Arber DA, Orazi A, Hasserjian R, Thiele J, Borowitz MJ, Le Beau MM, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127: 2391–2405. doi:10.1182/blood-2016-03-643544
No molecular abnormalities or diagnostic characteristics of another MPN or MPN/MDS
If a CSF3R mutation is NOT identified, the diagnosis of CNL can still be made if other reactive causes are excluded or other evidence of clonality is identified (persistent for at least 3 months). Continue reading Chronic Neutrophilic Leukemia (CNL)→
Does not meet the WHO criteria for another myeloid neoplasm
BM biopsy showing megakaryocytic proliferation
Enlarged mature megakaryocytes
Hyperlobated nuclei (not as pleomorphic or bizzare as in PMF)
Granulopoiesis and erythropoiesis is not increased or left shifted
No more than MF1 reticulin fibrosis
Minor Criteria
Evidence of a clonal marker or exclusion of reactive thrombocytosis
Diagnosis of ET is confirmed by all four major criteria, or if there is no evidence of a JAK2, CALR, or MPL mutation (major criterion #2), then the presence of the minor criterion.
Frequency of Molecular Abnormalities
JAK2 – 63% (V617F mutation)
CALR – 18%
MPL – 2-3%
Overall, approximately 83% of cases of ET have either a JAK2, CALR, or MPL mutation (n=79).
The use of immunohistochemistry (IHC) in many of the myeloproliferative neoplasms is limited. Identifying an increased blast population is one of the most useful, and may indicate a more aggressive course or transformation to acute leukemia. Helpful IHC markers may include:
CD117 is a specific myeloid marker, and marks a subset of myeloblasts. The expression is dim, and one often must look at 20-40X to clearly see expression. Mast cells (fried egg looking cell) will have very strong expression.
CD71 marks nucleated erythroid cells. This may be helpful in quantitating and differentiating erythroid cells from myeloid cells. This marker may be set-up as a double stain with CD34.
In the setting of hematopoietic cells, E-Cadherin marks immature erythroid cells. Like CD71, E-Cadherin may be useful to differentiate immature erythroid cells from immature myeloid cells.
TdT is a sensitive lymphoblast (~95%) marker. It is not entirely specific for lymphoblasts, but other markers can help clarify diagnostic difficulties (B and T-cell markers).
Arber DA, Orazi A, Hasserjian R, Thiele J, Borowitz MJ, Le Beau MM, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127: 2391–2405. doi:10.1182/blood-2016-03-643544
Kim SY, Im K, Park SN, Kwon J, Kim J-A, Lee DS. CALR, JAK2, and MPL mutation profiles in patients with four different subtypes of myeloproliferative neoplasms: primary myelofibrosis, essential thrombocythemia, polycythemia vera, and myeloproliferative neoplasm, unclassifiable. Am J Clin Pathol. 2015;143: 635–644. doi:10.1309/AJCPUAAC16LIWZMM
Diffuse increase of reticulin fibers with increased density and numerous intersections. Increased thick bundles of fibers consistent with collagen fibrosis. Osteosclerosis usually present.
In cases of MF2 or MF3, it is recommended to perform trichrome stain to evaluate for collagen fibrosis.
MF – Accelerated phase = 10-19% blasts in the peripheral blood and/or the bone marrow.
MF – Acute Transformation = ≥20% blasts in the blood or bone marrow.
Treatment – JAK 1/2 inhibitor ruxolitinib/Jakafi®
Photomicrographs
Immunohistochemistry
The use of immunohistochemistry (IHC) in many of the myeloproliferative neoplasms is limited. Identifying an increased blast population is one of the most useful, and may indicate a more aggressive course or transformation to acute leukemia. Helpful IHC markers may include:
CD117 is a specific myeloid marker, and marks a subset of myeloblasts. The expression is dim, and one often must look at 20-40X to clearly see expression. Mast cells (fried egg looking cell) will have very strong expression.
CD71 marks nucleated erythroid cells. This may be helpful in quantitating and differentiating erythroid cells from myeloid cells. This marker may be set-up as a double stain with CD34.
In the setting of hematopoietic cells, E-Cadherin marks immature erythroid cells. Like CD71, E-Cadherin may be useful to differentiate immature erythroid cells from immature myeloid cells.
TdT is a sensitive lymphoblast (~95%) marker. It is not entirely specific for lymphoblasts, but other markers can help clarify diagnostic difficulties (B and T-cell markers).
References
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
Arber DA, Orazi A, Hasserjian R, Thiele J, Borowitz MJ, Le Beau MM, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127: 2391–2405. doi:10.1182/blood-2016-03-643544
Kim SY, Im K, Park SN, Kwon J, Kim J-A, Lee DS. CALR, JAK2, and MPL mutation profiles in patients with four different subtypes of myeloproliferative neoplasms: primary myelofibrosis, essential thrombocythemia, polycythemia vera, and myeloproliferative neoplasm, unclassifiable. Am J Clin Pathol. 2015;143: 635–644. doi:10.1309/AJCPUAAC16LIWZMM
Tefferi A, Lasho TL, Finke CM, Knudson RA, Ketterling R, Hanson CH, et al. CALR vs JAK2 vs MPL-mutated or triple-negative myelofibrosis: clinical, cytogenetic and molecular comparisons. Leukemia. 2014;28: 1472–1477. doi:10.1038/leu.2014.3