Category Archives: Bone Marrow

Organ Systems, Bone Marrow, Lymph Node, WHO Classification

Follicular Lymphoma

Follicular Lymphoma (FL) is a mature B-cell lymphoma, which recapitulates or resembles germinal center B-cells.  Most cases (~85%) harbor the characteristic t(14;18), which juxtaposes the BCL-2 gene on chromosome 18 with the IgH gene on chromosome 14 (and hence BCL-2 IHC protein expression).  Most patients (~80-85) will present with advanced disease (stage III/IV), and bone marrow involvement is found in ~40% of cases with characteristic paratrabecular aggregates (mantle cell lymphoma and lymphoplasmacytic lymphoma may also have paratrabecular lymphoid aggregates).  Most of the cases that lack the t(14;18) IgH/BCL-2 translocation (and are BCL-2 negative) are typically grade 3 FLs with a BCL-6 translocation (~10-15%).  BCL-6 translocations can be evaluated for by FISH analysis, but the finding is NOT specific for FL.
 
Over time 30-50% of cases transform to diffuse large B-cell lymphoma (DLBCL).  In a small subset of transformations, a second “hit” with a MYC translocation will occur resulting in a very aggressive high grade large B-cell lymphoma: the so-called “double hit” lymphoma. 
Morphology
FL usually has at least a component of nodularity (+/- diffuse areas).  There are two cell types that make up FL, centrocytes and centroblasts.  Centrocytes are small cleaved cells with folded irregular nuclei.  Centorblasts are large cells with more open chromatin, multiple nucleoli, and more cytoplasm compared to centrocytes.  
 
Sometimes FL can have patterns that resemble marginal zone lymphoma, and can even have plasmacytic differentiation.  Therefore, it is important that a panel of markers be used to identify (or exclude) evidence of germinal center differentiation.  Occasional cases can have Hodgkin-like cells.
Immunophenotype 
Marker
Comment
Negative
Positive
Positive
Positive
  • Grade 1 – ~90%
  • Grade 2 – ~70%
  • Grade 3 – ~60%
Positive (~90%), negative cases do not contain the t(14;18), which is more common in grade 3 cases
  • Grade 1 – >90% + for BCL-2
  • Grade 2 – >80% + for BCL-2
  • Grade 3 – 50-70% + BCL-2
Positive, (~88%)
CD35
Highlights the follicular dendritic meshwork associated with FL.
Usually negative, higher grade lesions may be positive
Variable, shows low expression in low-grade processes, in distinct contrast to the high proliferation index and polarity associated with reactive germinal centers.
Negative
 
  
FL is typically expresses CD19, CD20, CD10, Bcl-6, and BCL-2 (~90%).  CD5 is not expressed in FL.  
  • Normal reactive germinal centers do not express Bcl-2.  In 90% of cases of FL, bcl-2 is expressed, which serves as a diagnostic tissue marker in lymphoma sections.
  • CD23 expression by flow cytometry has been associated with lower grade FLs (e.g. grade 1 & 2) and better survival.
Grading
  • Grade 1 & 2:  <= 15 centroblasts/HPF (based on 0.159 mm² HPF)
  • Grade 3:  > 15 centroblasts/HPF (based on 0.159 mm² HPF)
    • 3A:  Centrocytes present in the background
    • 3B:  NO centrocytes present in the background (not associated with the IgH/BCL-2 rearrangement, and usually lacks expression of CD10 and BCL-2; often MUM-1+)
Grade 1 & 2 behave in a similar fashion as a low grade lymphoma.  Grade 3 FL behaves as an intermediate grade lymphoma.  Grading of FL with counting of large cells must take into consideration the field diameter of the microscope being used.  The counts above are based on a F.N. 18 (0.159 mm² @ 40X).  Most convention pathology scopes today are F.N. 22 (0.247 mm² @ 40X), and adjustments are necessary.
Pattern
  • Predominately follicular:  >75% follicular/nodular architecture
  • Follicular and diffuse:  25-75% Diffuse areas or follicular/nodular architecture
  • Preominately diffuse:  <25% follicular/nodular areas (diffuse areas of otherwise grade 3 FL, then that component should be described as a separate component of diffuse large B-cell lymphoma)
Special Subtypes 
  • Large B-Cell Lymphoma with IRF4 Rearrangement
  • Pediatric Follicular Lymphoma
    • Occurs in children and young adults with an excellent prognosis, marked male predilection
    • The morphology is high-grade (FL grade 3) appearing
      • BCL-2 negative, lacK t(14;18)
      • CD10 + (usually)
      • MUM-1 negative
    • Associated with TNFRSF14 deletions of mutations
    • Localized process, usually in the head and neck area
  • Duodenal Follicular Lymphoma
    • Localized lesion
    • Grade 1-2 pattern
    • CD10/BCL-2 +
    • t(14;18) present
    • Lacks follicular dendritic meshwork
    • Ki-67, low expression
    • Excellent prognosis
  • Predominately Diffuse Follicular Lymphoma with 1p36 deletion
    • Localized mass (often inguinal)
    • Diffuse pattern, grade 1/2 
    • Excellent prognosis
    • Immunophenotype:  CD20+, CD10+, BCL-2+, BCL-6+, CD23+ (subset of cases)
    • t(14;18) NOT present
    • 1p36 deletion (not specific)
    • Lacks Bcl-2 rearrangement
  • Primary Cutaneous Follicular Lymphoma 
  • In Situ Follicular Neoplasm (ISFN)
References
Robbins and Cotran Pathologic Basis of Disease.  V Kumar, et al. 9th Edition. Elsevier Saunders. 2015. pp. 594-595.
 
Fedoriw Y, Dogan A. The Expanding Spectrum of Follicular Lymphoma. Surg Pathol Clin. 2016;9: 29–40. doi:10.1016/j.path.2015.11.001
 
Swerdlow SH, Campo E, Pileri SA, Harris NL, Stein H, Siebert R, et al. The 2016 revision of the World Health Organization classification of lymphoid neoplasms. Blood. 2016;127: 2375–2390. doi:10.1182/blood-2016-01-643569
 
Xerri L, Dirnhofer S, Quintanilla-Martinez L, Sander B, Chan JKC, Campo E, et al. The heterogeneity of follicular lymphomas: from early development to transformation. Virchows Arch. 2016;468: 127–139. doi:10.1007/s00428-015-1864-y
 
MD DY-PW, BacSc F. A case of t (14; 18)-negative follicular lymphoma with atypical immunophenotype: usefulness of immunoarchitecture of Ki67, CD79a and follicular dendritic cell …. … Malaysian journal of …. 2014.
 
Boyd SD, Natkunam Y, Allen JR, Warnke RA. Selective immunophenotyping for diagnosis of B-cell neoplasms: immunohistochemistry and flow cytometry strategies and results. Appl Immunohistochem Mol Morphol. 2013;21: 116–131. doi:10.1097/PAI.0b013e31825d550a
 
Cook JR. Nodal and leukemic small B-cell neoplasms. Mod Pathol. 2013;26 Suppl 1: S15–28. doi:10.1038/modpathol.2012.180
 
Olteanu H, Fenske TS, Harrington AM, Szabo A, He P, Kroft SH. CD23 Expression in Follicular Lymphoma: Clinicopathologic Correlations. Am J Clin Pathol. 2011;135: 46–53. doi:10.1309/AJCP27YWLIQRAJPW
 
Gradowski JF, Jaffe ES, Warnke RA, Pittaluga S, Surti U, Gole LA, et al. Follicular lymphomas with plasmacytic differentiation include two subtypes. Mod Pathol. 2010;23: 71–79. doi:10.1038/modpathol.2009.146
 
Katzenberger T, Kalla J, Leich E, Stöcklein H, Hartmann E, Barnickel S, et al. A distinctive subtype of t(14;18)-negative nodal follicular non-Hodgkin lymphoma characterized by a predominantly diffuse growth pattern and deletions in the chromosomal region 1p36. Blood. 2009;113: 1053–1061. doi:10.1182/blood-2008-07-168682
 
Bayerl MG, Bentley G, Bellan C, Leoncini L, Ehmann WC, Palutke M. Lacunar and reed-sternberg-like cells in follicular lymphomas are clonally related to the centrocytic and centroblastic cells as demonstrated by laser capture microdissection. Am J Clin Pathol. 2004;122: 858–864. doi:10.1309/PMR8-6PHK-K4J3-RUH3
Organ Systems, Bone Marrow, Lymph Node, WHO Classification

Lymphomatoid Granulomatosis

Lymphomatoid Granulomatosis (LYG) is a B-cell neoplasm of EBV + B-cells with characteristic anglocentric and angiodestructive features typically associated with some form of immunodeficiency.
 
LYG is an uncommon lymphoproliferative disorder and is not usually found in lymph nodes or spleen.  Pulmonary involvement is present in >90% of cases, and other organs (e.g. brain, kidney, skin, liver) can be variably affected.  
Morphology
LYG can have a varied appearance, but usually has a predominate background of small lymphocytes (T-cells), plasma cells, and histiocytes.  Eosinophils and neutrophils are not a typical finding.  Neoplastic EBV + B-cells can have a variable appearance ranging from immunoblast-like cells to morphologies similar to Hodgkin cells.  The lymphoid infiltrate has an anglocentric and angiodestructive pattern, which may result in necrosis.  If the pattern is of large cells in diffuse sheets, then the diagnosis of EBV+ diffuse large B-cell lymphoma should be made.
 
Differential diagnosis – Extranodal NK/T-cell lymphoma, nasal type is also an EBV+ tumor with an angiodestructive growth pattern.
Immunophenotype
  • EBV+ Neoplastic B-cells
  • CD20+
  • CD30 variably positive
  • Background T-cells
Grading
  • Grade 1 – < 5 EBV+ cells/HPF, polymorphic lymphoid infiltrate (large atypical cells rare/absent), No/focal necrosis.
  • Grade 2 – 5-20 EBV+ cells/HPF (small clusters of B-cells by CD20), occasional large atypical/transformed cells.
  • Grade 3 – > 50 EBV+ cells/HPF, numerous large atypical CD20+ B-cells (may form large aggregates)
References
WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues.  SH Swerdlow, et al. International Agency for Research on Cancer. Lyon, 2008. p. 247-249
Organ Systems, Bone Marrow, WHO Classification

Hairy Cell Leukemia

Hairy cell leukemia (HCL) is an uncommon (2% of lymphomas) but distinctive B-cell lymphoproliferative disease.  Clinically, patients present with hepatosplenomegaly and pancytopenia usually with a marked moncytopenia.  Classically, hairy cell leukemia has been difficult to differentiate from hairy cell variant (HCL-v) and splenic marginal zone lymphoma (SMZL).  There has been significant morphologic, clinical and immunophenotypic overlap between these entities.  An accurate diagnosis is critical as HCL is treated very differently (purine analogs) than other lymphomas with a high cure rate (>90%).  Purine analog chemotherapy regimen is also much easier to tolerate than other chemotherapy protocols.
Morphology
HCL is characterized by small lymphoid cells with moderate to abundant cytoplasm (cells may be mistaken for erythroid precursors or other cells in the bone marrow trephine biopsy), which have an interstitial marrow pattern of involvement (morphologic estimate of involvement is often markedly underestimated compared to CD20 staining).  Reticulin fibrosis is also characteristic, which often results in a “dry tap” (unable to obtain a bone marrow aspirate).  Peripheral blood can show variable invovelemnt with characteristic “hair-like” cytoplasmic projections.  It is very uncommon to have lymph node involvement.
Immunophenotype  
  • CD19/CD20 +
  • CD25/CD103 + (CD25 co-expression with CD103 appears to be specific for HCL relative to the differential diagnosis with HCL-v and SMZL)
  • Annexin A1 +
  • CD11c +
  • TRAP +
  • DBA.44 + (thought to be specific for HCL when combined with TRAP +)
  • CD5 – (rare cases <5% may be CD5+ by flow cytometry)
  • CD10 -/+ (approximately 30% of cases may express CD10 by flow cytomtetry)
  • BRAF VE1 (IHC) +
Molecular 
  • >90% found to have a BRAF V600E mutation.  This can be identified by PCR or immunohistochemistry (IHC may be more sensitive than PCR).  This appears to be relatively specific (relative to the usual differential diagnosis of HCL) with only rare cases of CLL/SLL, marginal zone lymphoma, and multiple myeloma found to express BRAF V600E IHC stain.
  • MAP2K1 mutations (encodes MEK1 downstream of BRAF) in most BRAF negative HCL cases that use IgHV4-34.  This mutation finding is not specific to HCL and may be seen in hairy cell variant (HCL-v).
References
Swerdlow SH, Campo E, Pileri SA, Harris NL, Stein H, Siebert R, et al. The 2016 revision of the World Health Organization classification of lymphoid neoplasms. Blood. 2016;127: 2375–2390. doi:10.1182/blood-2016-01-643569
 
Uppal G, Ly V, Wang ZX, Bajaj R, Solomides CC, Banks PM, et al. The Utility of BRAF V600E Mutation-Specific Antibody VE1 for the Diagnosis of Hairy Cell Leukemia. Am J Clin Pathol. 2014;143: 120–125. doi:10.1309/AJCPQLQ89VXTVWKN
 
Brown NA, Betz BL, Weigelin HC, Elenitoba-Johnson KSJ, Lim MS, Bailey NG. Evaluation of Allele-Specific PCR and Immunohistochemistry for the Detection of BRAF V600E Mutations in Hairy Cell Leukemia. Am J Clin Pathol. 2014;143: 89–99. doi:10.1309/AJCPDN4Q1JTFGCFC
 
Boyd SD, Natkunam Y, Allen JR, Warnke RA. Selective immunophenotyping for diagnosis of B-cell neoplasms: immunohistochemistry and flow cytometry strategies and results. Appl Immunohistochem Mol Morphol. 2013;21: 116–131. doi:10.1097/PAI.0b013e31825d550a
 
Robbins and Cotran Pathologic Basis of Disease.  V Kumar, et al. 9th Edition. Elsevier Saunders. 2015. pp. 603-604.
 
Turakhia S, Lanigan C, Hamadeh F, Swerdlow SH, Tubbs RR, Cook JR. Immunohistochemistry for BRAF V600E in the Differential Diagnosis of Hairy Cell Leukemia vs Other Splenic B-Cell Lymphomas. Am J Clin Pathol. 2015;144: 87–93. doi:10.1309/AJCP5WVXJ2KTLODO
 
Andrulis M, Penzel R, Weichert W, Deimling von A, Capper D. Application of a BRAF V600E mutation-specific antibody for the diagnosis of hairy cell leukemia. Am J Surg Pathol. 2012;36: 1796–1800. doi:10.1097/PAS.0b013e3182549b50
Organ Systems, Bone Marrow, Lymph Node, WHO Classification

Lymphoplasmacytic Lymphoma (LPL)

Lymphoplasmacytic Lymphoma (LPL)
  • Neoplastic proliferation of B-cells ranging in spectrum from lymphocytes to plasma cells (typically involves the bone marrow, but can also involve the spleen and lymph nodes).  
  • Bone marrow involvement
    • Nodular, diffuse, and/or interstitial
    • Small lymphocytes admixed with plasma cells and plasmacytoid lymphocytes
  • IgM paraprotein
    • Sometimes result in a hyperviscosity syndrome(30%)
    • IgM and IgG paraprotein (minority)
    •  Some cases may be IgG or IgA. 
  • Cryoglobulinemia (20% of WM)
  • Coagulopathy (IgM binds to clotting factors)
  • MYD88 (L265P) point mutation (>90%)
    • Results in up-regulation of NF-κB (promotes tumor cell survival). 
    • Not specific for LPL.
  • LPL is a diagnosis of exclusion after other B cell lymphoid neoplasms with plasmacytic differentiation have been excluded.  
  • IgM MGUS is now thought to be more closely related to LPL than plasma cell myeloma.

Most patients present with non-specific B-symptoms.  However, ~10% have hemolysis secondary to cold agglutinins (IgM binds to RBCs at temperature <37C).

Waldenstrom macroglobulinemia
Waldenstrom macroglobulinemia (defined as bone marrow involvement by LPL and IgM monoclonal gammopathy) may manifest as a hyperviscosity syndrome due to the circulating IgM in the blood (IgM tends to stay in the vascular system, compared to IgG which can penetrate into soft tissue).  Because IgM molecules tend to be well-segregated to the vascular compartment, plasmapheresis can be very effective to treat hyerpviscosity symptoms.  Clinical signs/symptoms include:
  • Cryoglobulinemia – precipitation of macroglobulins as temperatures <37C
  • Bleeding – macroglobulins interfere with clotting factors
  • Neurologic disturbances – secondary to increased blood viscosity
  • Visual impairment – secondary to increased viscosity and hemorrhage
Immunophenotype
Marker
Comment
Negative
Negative (~10% +)
Negative
Positive
Negative (rare atypical cases +)
Positive (best marker).  Marks from Mature B-Cells through Plasma Cell differentiation.
Often Positive
Positive
Negative
Positive
Morphology
The bone marrow can have a varying degree of involvement (usually interstitial to nodular) by tumor cells showing a range from small lymphocytes to plasmacytoid lymphocytes to plasma cells.  Mast cell hyperplasia is commonly present.
 
Lymphoplasmacytic Lymphoma (LPL) - Aspirate Smear
Lymphoplasmacytic Lymphoma (LPL) – Aspirate Smear
Lymphoplasmacytic Lymphoma (LPL) - CD138
Lymphoplasmacytic Lymphoma (LPL) – CD138
Lymphoplasmacytic Lymphoma (LPL) - BM Core Biopsy
Lymphoplasmacytic Lymphoma (LPL) – BM Core Biopsy.  Plasma cells (not obvious) admixed with small lymphoid infiltrate.
References
Robbins and Cotran Pathologic Basis of Disease.  V Kumar, et al. 9th Edition. Elsevier Saunders. 2015. pp. 601-602.
 
Harmon CM, Smith LB. B-cell Non-Hodgkin Lymphomas with Plasmacytic Differentiation. Surg Pathol Clin. 2016;9: 11–28. doi:10.1016/j.path.2015.09.007
 
WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues.  SH Swerdlow, et al. International Agency for Research on Cancer. Lyon, 2008. p. 194-195
 
Swerdlow SH, Campo E, Pileri SA, Harris NL, Stein H, Siebert R, et al. The 2016 revision of the World Health Organization classification of lymphoid neoplasms. Blood. 2016;127: 2375–2390. doi:10.1182/blood-2016-01-643569
 
Martinez-Lopez A, Curiel-Olmo S, Mollejo M, Cereceda L, Martinez N, Montes-Moreno S, et al. MYD88 (L265P) somatic mutation in marginal zone B-cell lymphoma. Am J Surg Pathol. 2015;39: 644–651. doi:10.1097/PAS.0000000000000411
 
Treon SP, Xu L, Yang G, Zhou Y, Liu X, Cao Y, et al. MYD88 L265P somatic mutation in Waldenström’s macroglobulinemia. N Engl J Med. 2012;367: 826–833. doi:10.1056/NEJMoa1200710
 
Bone Marrow IHC.  Torlakovic, EE, et. al. American Society for Clinical Pathology Pathology Press © 2009.  pp. 27.
 
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011. pp.194-195.
Organ Systems, Bone Marrow, Lymph Node, WHO Classification

MYD88 (L265P) Mutation

MYD88 (L265P) mutation has garnered a lot of excitement because of its usefulness in diagnosing lymphoplasmacytic lymphoma (LPL).  Traditionally, LPL has been difficult to diagnose because exclusion of other B-cell neoplasms with plasmacytic differentiation is required. MYD88 mutations are present in approximately 90% of cases of LPL, and in a much lower percentage of cases of B cell lymphomas, which are typically in the differential diagnosis of LPL.
 MYD88 mutation frequency
References
Harmon CM, Smith LB. B-cell Non-Hodgkin Lymphomas with Plasmacytic Differentiation. Surg Pathol Clin. 2016;9: 11–28. doi:10.1016/j.path.2015.09.007
 
WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues.  SH Swerdlow, et al. International Agency for Research on Cancer. Lyon, 2008. p. 194-195
 
Swerdlow SH, Campo E, Pileri SA, Harris NL, Stein H, Siebert R, et al. The 2016 revision of the World Health Organization classification of lymphoid neoplasms. Blood. 2016;127: 2375–2390. doi:10.1182/blood-2016-01-643569
 
Martinez-Lopez A, Curiel-Olmo S, Mollejo M, Cereceda L, Martinez N, Montes-Moreno S, et al. MYD88 (L265P) somatic mutation in marginal zone B-cell lymphoma. Am J Surg Pathol. 2015;39: 644–651. doi:10.1097/PAS.0000000000000411
 
Treon SP, Xu L, Yang G, Zhou Y, Liu X, Cao Y, et al. MYD88 L265P somatic mutation in Waldenström’s macroglobulinemia. N Engl J Med. 2012;367: 826–833. doi:10.1056/NEJMoa1200710