Category Archives: Organ Systems

Lymph Node, WHO Classification

In Situ Follicular Neoplasia (ISFN)

In Situ Follicular Neoplasia (ISFN), which has been previously referred to as Follicular Lymphoma Is Situ (FLIS) is found in approximately 2% of otherwise reactive lymph nodes.  ISFN is defined as partial to total colonization of germinal centers by B-cells containing the t(14;18) BCL-2/IgH translocation characteristic of follicular lymphoma.

ISFN found as an incidental finding have a risk of developing follicular lymphoma (FL) of <= 5%.  The amount of involvement of ISFN within a lymph node does not appear to be directly related to the risk of future FL.

If patients have other evidence of lymphadenopathy, then additional biopsies may be helpful to exclude a B-cell lymphoma at another site.

Morphology

H&E staining demonstrates normal appearing lymph node architecture with well-formed and well-demarcated germinal centers.  Follicles with ISFN at first glance do not look significantly different from the adjacent reactive follicles.  Some areas of ISFN may more prominent and closely associated centrocytes (subtle).

Immunohistochemistry

  • CD10 – Strong expression
  • Bcl-6 – Positive
  • Bcl-2 – Positive (often stronger expression than surrounding lymphocytes)
  • Ki-67 – Usually significantly lower expression than that of adjacent reactive germinal centers
  • CD20 – Positive

Photomicrographs

H&E section containing ISFN. Morphologically the node appears consistent with an otherwise reactive lymph node.
H&E section of ISFN.
CD3 expression in ISFN.
CD20 expression in a follicle containing ISFN.
CD10 expression in ISFN.
Bcl-6 expression in ISFN. Note the crowding of centrocytes highlighted by the Bcl-6 positive cells.
Strong Bcl-2 expression in the ISFN. Note the brighter expression compared to the surrounding T-cells and mantle zone. An adjacent reactive follicle is negative for Bcl-2.
Low Ki-67 expression in ISFN (left side of image) compared to the high proportion of cell expression in the reactive follicle on the right.

Differentiating from partial involvement by follicular lymphoma

Sometimes it can be difficult to differentiate partial involvement of a lymph node by FL from ISFN.  The following features are helpful to differentiate partial involvement by FL from ISFN:

  • ISFN – Intact nodal architecture 
  • Partial involvement by FL – Altered architecture on H&E sections
  • ISFN – Normal sized follicles
  • Partial involvement by FL – Often enlarged follicles
  • ISFN – Sharp border between the follicle center and the surrounding mantle zone
  • Partial involvement by FL – Interface between the follicle center and mantle zone is often fuzzy or blurred.
  • ISFN – Bcl-2 is strongly positive (usually brighter than the surrounding T-cells and mantle zones); CD10 strongly positive
  • Partial involvement by FL – variable Bcl-2 and CD10 expression
  • ISFN – Atypical cells are confined to the follicle center
  • Partial involvement by FL – atypical cells (CD10/bcl2+) can be found outside of the follicle center areas

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

Gynecological, Uterus

FIGO Grading

The International Federation of Gynecology and Obstetrics (FIGO) grading system for endometrial endometrioid carcinoma:

  • FIGO Grade 1:  <=5% solid, non-glandular, non-squamous growth
  • FIGO Grade 2:  6-50% solid, non-glandular, non-squamous growth
  • FIGO Grade 3:  >50% solid, non-glandular, non-squamous growth

Marked cytologic atypia increases the grade by 1.

FIGO Grading is only performed on endometrioid and mucinous adenocarinomas.  Other tumor subtypes (clear cell, serous, carcinomasarcomas) carry their own associated grade.  Mucinous adenocarcinomas are considered to be closely related to endometrioid carcinomas.

References

  1. Soslow RA, Tornos C, Park KJ, Malpica A, Matias-Guiu X, Oliva E, et al. Endometrial Carcinoma Diagnosis: Use of FIGO Grading and Genomic Subcategories in Clinical Practice: Recommendations of the International Society of Gynecological Pathologists. Int J Gynecol Pathol. 2019;38 Suppl 1: S64–S74. doi:10.1097/PGP.0000000000000518
Lymph Node, Pulmonary, WHO Classification

DLBCL Associated with Chronic Inflammation

DLBCL associated with chronic inflammation is a special subtype of DLBCL first described in 1987 and subsequently recognized as a specific and separate entity in the 2008 WHO hematopathology classification.

Morphologically, it is recognized as a diffuse large B-cell lymphoma that arises in the setting of long-standing chronic inflammation and is associated with EBV infection. Commonly, these present as tumor masses involving body cavities. This is classically and originally described as pleural-based lesions in patients with chronic pyothorax (artificial pneumothorax for pulmonary tuberculosis or tuberculosis pleuritis).

Originally, these were designated as ‘pyothorax-associated lymphomas’ (PAL) and characteristically are associated with EBV.  It is thought that these lesions arise as a result of ‘local’ immunodeficiency, and seem to carry the following common characteristics (regardless of location):

  1. Association with EBV
  2. Confined space (often body cavity)
  3. Long standing/slow growing lesion associated with chronic inflammation
  4. Morphologic characteristics of diffuse large B-cell lymphoma
Immunophenotype

Often, these cases will have extensive necrosis, which may make diagnosis very difficult on small biopsy samples. Additionally, the immunophenotype may vary widely with variable loss and expression of both T and B cell markers.

  • CD20 +
  • CD79a +
  • MUM-1 +
  • CD138 +/-(these cases may be negative for CD20/CD79a)
  • Subset of cases with T-cell marker expression (CD2, CD3, CD4, and/or CD7)
  • EBV (EBER) +
Microscopic images
DLBCL associated with chronic inflammation
DLBCL associated with chronic inflammation – Extensive necrosis
DLBCL associated with chronic inflammation
Aberrant CD3 expression in DLBCL associated with chronic inflammation
Aberrant strong CD7 expression in DLBCL associated with chronic inflammation
Strong CD20 expression in DLBCL associated with chronic inflammation
Dim subset expression of CD79a in DLBCL associated with chronic inflammation.
Strong diffuse MUM-1 expression in DLBCL associated with chronic inflammation
EBER expression (strong/diffuse) in neoplastic cells of DLBCL associated with chronic inflammation.
References

Loong F, Chan ACL, Ho BCS, Chau Y-P, Lee H-Y, Cheuk W, et al. Diffuse large B-cell lymphoma associated with chronic inflammation as an incidental finding and new clinical scenarios. Mod Pathol. 2010;23: 493–501. doi:10.1038/modpathol.2009.168


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

Bone Marrow, MDS, MDS/MPN, MPN

Myelofibrosis – Etiologies

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.

Infectious diseases
  • Tuberculosis
Autoimmune disorders
  • Systemic lupus erythematosus (SLE)
  • Sjogren’s syndrome (SS)
  • Systemic sclerosis
  • Primary autoimmune myelofibrosis
  • Connective tissue disease
Drug associated conditions
  • Thrombopoietin receptor agonist toxicity
Endocrine disorders
  • Hyperparathyroidism (primary or secondary)
  • Vitamin D deficiency (nutritional or rickets)
  • Osteomalacia
Hematologic malignancies
Other hematologic malignancies
  • Paroxysmal nocturnal hemoglobinuria (PNH)
  • Gray platelets syndrome
Other
  • Primary hypertrophic osteoarthropathy
  • Paget disease
  • Metastatic solid tumor malignancies
Myelofibrosis Grading
Grade
Comment
Scattered linear fibers without intersections.  Normal bone marrow.
MF1
Loose network of reticulin fibers with intersections (particularly perivascular)
Diffuse increase of reticulin fibers with increased density and numerous intersections.  Focal bundles of thick fibers.
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.

Antibody List, N - Z Antibodies, Pulmonary

ROS-1

ROS-1 rearrangements with at least 12 different partner proteins have been identified in a small subset of lung non-small cell carcinomas (1–2%), which shows susceptibility to tyrosine kinase inhibitors (TKIs) similar to ALK rearranged tumors.  ROS-1 is considered a oncogene found on chromosome 6.  The exact mechanism of activation of this gene protein product with the various gene rearrangement partners is not understood.  The protein function is similar to that of the ALK family, which is why this mutation was studied for possible response to ALK inhibitors (crizotinib).
 
Recently, ROS-1 mutated tumors have been approved for TKI therapy with identification of a rearrangement by FISH analysis.  Like ALK, ROS-1 FISH utilizes a break apart probe to identify the presence of a gene rearrangement.  Other successful modalities for identification of ROS-1 rearrangements include ‘next generation’ sequencing (NGS) and immunohistochemistry.
 
Immunohistochemistry (IHC) has been studied as an alternative to FISH as a screening modality.  Based on multiple studies, the sensitivity of IHC appears to be near 100% with the specificity of at least 92%.  These studies were performed using the D4D6 rabbit monoclonal antibody clone (Cell Signaling Technology, Danvers, Massachusetts).
Stain Interpretation
Unlike ALK, there is no known normal tissue counterpart which can be used as a control.  Therefore, known ROS-1 positive tumors or cell lines  (HCC78 cell line with the SLC34A2-ROS1 rearrangement) are generally used.  ROS-1 expression is cytoplasmic with described expression ranging from finely granular to globular cytoplasmic staining and membranous staining.  No consensuses has been established as to the minimal threshold of positivity.
 
Possible interpretation pitfalls include weak staining of type II pneumocytes and alveolar macrophages along with osteoclast-type giant cells in bone biopsies.  Like any immunostain, contextual evaluation is critical.
References
Thunnissen E, Allen TC, Adam J, Aisner DL, Beasley MB, Borczuk AC, et al. Immunohistochemistry of Pulmonary Biomarkers: A Perspective From Members of the Pulmonary Pathology Society. Arch Pathol Lab Med. 2018;142: 408–419. doi:10.5858/arpa.2017-0106-SA
 
Shaw AT, Ou S-HI, Bang Y-J, Camidge DR, Solomon BJ, Salgia R, et al. Crizotinib in ROS1-rearranged non-small-cell lung cancer. N Engl J Med. 2014;371: 1963–1971. doi:10.1056/NEJMoa1406766
 
Bubendorf L, Büttner R, Al-Dayel F, Dietel M, Elmberger G, Kerr K, et al. Testing for ROS1 in non-small cell lung cancer: a review with recommendations. Virchows Arch. 2016;469: 489–503. doi:10.1007/s00428-016-2000-3
 
Boyle TA, Masago K, Ellison KE, Yatabe Y, Hirsch FR (2015) ROS1 immunohistochemistry among major genotypes of non- small-cell lung cancer. Clin Lung Cancer 16(2):106–111. doi:10.1016/j.cllc.2014.10.003 
 
CaoB,WeiP,LiuZ,BiR,LuY,ZhangL,ZhangJ,YangY,Shen C, Du X, Zhou X (2016) Detection of lung adenocarcinoma with ROS1 rearrangement by IHC, FISH, and RT-PCR and analysis of its clinicopathologic features. Onco Targets Ther 9:131–138. doi:10.2147/OTT.S94997 
 
Sholl LM, Sun H, Butaney M, Zhang C, Lee C, Janne PA, Rodig SJ (2013) ROS1 immunohistochemistry for detection of ROS1-rearranged lung adenocarcinomas. Am J Surg Pathol 37(9):1441–1449. doi:10.1097/PAS.0b013e3182960fa7
 
Yoshida A, Tsuta K, Wakai S, Arai Y, Asamura H, Shibata T, Furuta, K, Kohno T, Kushima R (2014) Immunohistochemical detection of ROS1 is useful for identifying ROS1 rearrangements in lung can- cers. Mod Pathol 27(5):711–720. doi:10.1038/modpathol.2013.192
 
Rogers TM, Russell PA, Wright G, Wainer Z, Pang JM, Henricksen LA, Singh S, Stanislaw S, Grille J, Roberts E, Solomon B, Fox SB (2015) Comparison of methods in the detection of ALK and ROS1 rearrangements in lung cancer. J Thorac Oncol 10(4):611–618. doi:10.1097/JTO.0000000000000465
 
Rimkunas VM, Crosby KE, Li D, Hu Y, Kelly ME, Gu TL, Mack JS, Silver MR, Zhou X, Haack H (2012) Analysis of receptor tyro- sine kinase ROS1-positive tumors in non-small cell lung cancer: identification of a FIG-ROS1 fusion. Clin Cancer Res 18(16): 4449–4457. doi:10.1158/1078-0432.CCR-11-3351
 
Mescam-Mancini L, Lantuejoul S, Moro-Sibilot D, Rouquette I, Souquet PJ, Audigier-Valette C, Sabourin JC, Decroisette C, Sakhri L, Brambilla E, McLeer-Florin A (2014) On the relevance of a testing algorithm for the detection of ROS1-rearranged lung adenocarcinomas. Lung Cancer 83(2):168–173. doi:10.1016/j. lungcan.2013.11.019 
 
Shan L, Lian F, Guo L, Qiu T, Ling Y, Ying J, Lin D (2015) Detection of ROS1 gene rearrangement in lung adenocarcinoma: comparison of IHC, FISH and real-time RT-PCR. PLoS One 10(3): e0120422. doi:10.1371/journal.pone.0120422 
Organ Systems, Bone Marrow, WHO Classification, MDS/MPN

MDS/MPN-RS-T

 
Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) is a hybrid myeloproliferative and myelodysplastic neoplasm that contains thrombocytosis and ring sideroblasts.  There are also generally characteristic clinical and molecular abnormalities.
Diagnostic Criteria
  • Anemia with erythroid dysplasia (+/- multilineage dysplasia)
    • <1% blasts in the peripheral blood
    • <5% blasts in the bone marrow
    • ≥15% ring sideroblasts
  • Platelet count >/= 450 K, which is persistent
  • Does not meet the criteria for another hematopoietic neoplasm, specifically:
    • BCR–ABL1 negative
    • No PDGFRA, PDGFRB, FGFR1 rearrangements
    • PCM1–JAK2 negative
    • No t(3;3)(q21.3;q26.2), inv(3)(q21.3q26.2), or del(5q)
  • No history of a myeloproliferative and/or myelodysplastic neoplasm.  There is an exception for a previous history of MDS with ring sideroblasts (MDS–RS).
Clinical Features
  • Anemia: Usually milder than that typically associated with myelodysplasia
  • Splenomegaly is present in approximately 40% of cases
Molecular Features
  • Cytogenetic abnormalities – 10% of cases
  • SF3B1 mutation – 60-90% of cases
    • >60% of cases have JAK2 mutation
    • <10% of cases have associated CALR or MPL mutations
References
Gurevich I, Luthra R, Konoplev SN, Yin CC, Medeiros LJ, Lin P. Refractory anemia with ring sideroblasts associated with marked thrombocytosis: a mixed group exhibiting a spectrum of morphologic findings. Am J Clin Pathol. 2011;135: 398–403. doi:10.1309/AJCPT0B6VEQPRCOA
 
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
 
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
Organ Systems, Lymph Node, WHO Classification

Large B-Cell Lymphoma with IRF4 Rearrangement

This is a special subtype of B-cell lymphoma, which may have an entirely diffuse, diffuse and follicular, or exclusive follicular pattern.  It is typically characterized by strong IRF4/MUM-1 expression by immunohistochemistry.  An IRF4 rearrangement is typically found.  This lymphoma most commonly occurs in children or young adults in the head and neck region (especially Waldeyer ring).
 
Morphologically these cases would otherwise be characterized as a diffuse large B-cell lymphoma, follicular lymphoma, or combined follicular and diffuse large B-cell lymphoma.   In the pure follicular pattern, some have referred to this as “Waldeyer Ring Follicular Lymphoma.”  Suspicion should be raised based on the patient’s age, disease location, and coexpression of CD10 and MUM-1.
Immunophenotype
  • CD20 positive
  • CD79a positive
  • PAX-5 positive
  • MUM-1 strongly expressed
  • BCL-6 positive
  • PRDM1 (BLIMP1) typically negative
  • CD10 usually positive (66%)
  • BCL-2 usually positive (66%)
  • Ki-67 high (lack of evidence of polarization in neoplastic follicles)
Cases with a phenotype of CD10 coexpression with MUM-1 should be considered for IRF4 rearrangements screening.  The prognosis is relatively good with appropriate treatment.
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
 
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
 
Salaverria I, Philipp C, Oschlies I, Kohler CW, Kreuz M, Szczepanowski M, et al. Translocations activating IRF4 identify a subtype of germinal center-derived B-cell lymphoma affecting predominantly children and young adults. Blood. 2011;118: 139–147. doi:10.1182/blood-2011-01-330795
 
 
Organ Systems, Lymph Node, WHO Classification, Hematopathology

DLBCL – Anaplastic Variant

The anaplastic variant of diffuse large B-cell lymphoma (DLBCL) is a morphologic variant under the DLBCL, NOS category in the WHO Classification.  Typical common features include:

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