Haematopathology

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Understanding of haematopathology is important in anatomical pathology, as haematologic malignancies are often in the (clinical) differential diagnosis and may mimic small blue round cell tumours or lobular breast carcinoma.

The lymph node is discussed below; however, details are covered in the lymph node article and lymph node pathology article.

Bone marrow

Main article: Bone

Bone marrows are important for understanding haematopathology. They are dealt with in the bone article.

Normal lymph node

Main article: Lymph node
Main article: Lymph node pathology

Microscopic

The microscopic lymph node architecture in described the lymph node article, along with B cell maturation and lymph node cell types.

The cells of the lymph node:

  • Germinal center:
    • Centrocytes - cleaved nucleus.
    • Centroblasts - large dark, mitotically active, medullary aspect of germinal center.
    • Tingible body macrophages.
    • Follicular dendritic cells.
  • Paracortex:
    • T lymphocytes.
    • Interdigitating dendritic cells.
  • Mantle zone:
    • Immunoblasts (Memory B cells) - small lymphocytes.
  • Medulla:
    • B lymphocytes.
    • Plasma cells.

Hemophagocytic syndrome

Main article: Hemophagocytic syndrome

General

  • Rare.

Microscopic

Features:

  • Macrophages eat RBCs, WBCs.

Heparin-induced thrombocytopenia

  • Thrombocytopenia due to heparin.[1]

Classification:

  • Type 1 - in first two days of exposure - considered non-immune and considered not to be serious.
  • Type 2 - in the first 4-10 days - considered serious.

Diagnosis (simplified):

  • 50% decline in platelets - within 4-10 days of starting heparin.
  • HIT assay - several exist.[2]

Lymphoma classification

Lymphomas can be divided into:

  • Hodgkin's lymphoma.
  • Non-Hodgkin's lymphoma (NHL).

Other categorizations:

  • T cell lymphomas (rare).
  • B cell lymphomas (more common).

Two most common NHLs:

  • Follicular lymphoma (FL).
  • Diffuse large B-cell lymphoma (DLBCL).

Lymphoma as a med student

  • Acute lymphoid leukemia (ALL) - predominantly in smALL people, i.e. children.
  • Acute myeloid leukemia (AML).
  • Chronic myeloid leukemia (CML).
  • Chronic lymphoid leukemia (CLL) - relatively good prognosis.

Histologic classification

  1. "Size".
  2. Nodularity.

"Size"

  • The single most important factor for classifying lymphomas.
  • Not really based on size.
"Large" "Small" Utility
Nucleoli present absent most discriminative
Size >2x RBC dia. <2x RBC dia. moderate
Chromatin pattern "open" (pale) "closed" moderate/minimal
Cytoplasm mold-minimal
basophilic cytoplasm 		scant cytoplasm minimal

Histologic terms

  • Lymphomas = cells look discohesive, may be difficult to differentiate from poor differentiated carcinoma.
  • Auer rods = Acute myeloid leukemia.
    • Granular cytoplasmic rod (0.5-1 x4-6 micrometres).
  • Reed-Sternberg cells = Hodgkin's lymphoma.
    • Large cell - very large nucleus.
      • Classically binucleated.
  • Russell bodies = Plasmacytoma (+others).
    • Eosinophilic, large, homogenous immunoglobulin-containing inclusions.[3]
      • Mott cell is a cell that contains Russell bodies.[3]
  • Effacement of nodal architecture.
  • Loss of proliferation centers.

IHC

General

  • CD45.
    • AKA common lymphocyte antigen.
    • Useful to differentiate from carcinomas (e.g. small cell carcinoma).

T cell markers

  • CD2 -- T cell marker (all T cells).
  • CD3 -- T cell marker (all T cells).
    • CD4 -- subset of T cells.
    • CD8 -- subset of T cells.
  • CD7 -- often lost first in T cell lymphomas.
  • CD5 -- +ve in CLL & mantle cell lymphoma.
  • CD43 -- +ve in mantle cell lymphoma

B cell markers

  • CD20 -- B cell marker.
  • PAX-5.
  • CD79a.
  • CD10 -- follicule center.
  • BCL-6.
  • BCL-2.

Follicular dendritic cells

  • CD23 -- follicular dendritic cells.
  • CD21 -- follicular dendritic cells.

Hodgkin's lymphoma

Classic
  • CD30 -- Hodgkin's lymphoma (most sensitive).
  • CD15.

Hodgkin's lymphoma

Main article: Hodgkin's lymphoma

General

  • Abbreviated HL.

Microscopic

By definition, HL has Reed-Sternberg cells (RSCs).

Classical HL

Features (classic HL):

  • Reed-Sternberg cell.
    • Large binucleated cell.
    • Macronucleolus - approximately the size of a RBC (~8 micrometers).
    • Well-defined cell border.

Images (classic HL):

Subtypes

There are four CHL subtypes:[4]

  1. Nodular sclerosis CHL - ~70% of CHL.
    • Mixed cellular background - T cell, plasma cells, eosinophils, neutrophils and histiocytes.
    • Nodular sclerosing fibrosis - thick strands fibrosis.
  2. Mixed cellularity CHL - ~20-25% of CHL.
    • Like nodular sclerosis - but no fibrosis.
  3. Lymphocyte-rich CHL - rare.
    • T lymphocytes only (no mix of cells).
  4. Lymphocyte-depleted CHL - rare.
    • Assoc. with HIV infection.

Memory device:

  • The subtypes prevalence is in reverse alphabetical order.

Nodular lymphocyte-predominant HL

Features (nodular lymphocyte-predominant Hodgkin's lymphoma):

  • Lymphocytic & histiocytic cell (L&H cell)[5] - variant of RSC:
    • Cells (relatively) small (compared to classic RSCs).
    • Lobulated nucleus - key feature.
    • Small nucleoli.

Image (NLPHL):

Follicular lymphoma

Main article: Small cell lymphomas

Diffuse large B-cell lymphoma

Main article: Diffuse large B cell lymphoma

General

  • Abbreviated DLBCL.

Microscopic

Features:[6]

  • Large cells -- 4-5 times the diameter of a small lymphocytes.
  • Typically have marked cell-to-cell variation in size and shape.
  • Cytoplasm usu. basophilic and moderate in abundance.
  • +/-Prominent nucleoli, may be peripheral and/or multiple.

Notes:

  • Large bizarre cells can occasionally mimic Reed-Sternberg cells, seen in Hodgkin lymphoma.

Burkitt's lymphoma

General

  • Abbreviated BL.
  • Extremely high proliferative rate & rate of apoptosis.

Subtypes

  • Three subtypes recognized:[7]
  1. Endemic:
    • Found in Africa.
    • EBV (Epstein-Barr virus) associated.[7]
  2. Non-endemic:
    • Typical of the BL seen in the western world; EBV negative.
  3. Immunodeficiency associated:
    • Associated with HIV infection.

Pathophysiology

  • Origin cell: germinal centre B cells (favoured) vs. memory B cells.[7]
  • Common translocation t(8;14).[7]

Cytologic definition

  • t(8;14) (q24;q32) translocation + a few variants or c-myc rearrangement.[7]

Histology

  • "Starry-sky pattern".
    • The stars in the pattern are: tingible-bodies laden macrophages.
  • Tumour cells:[7]
    • Medium size.
    • Round nuclei.
    • Multiple nucleoli.
    • Relatively abundant cytoplasm.

Image: Starry-sky pattern - Ed Uthman (www.wikipedia.org).

Plasmacytoma

General

  • AKA plasma cell myleoma.
  • Malignancy derived from the plasma cells.
  • Histologic component of multiple myeloma; to diagnose multiple myeloma other (non-pathology) criteria are needed.
  • Prognosis: poor.

Microscopic

Features:

Images:

DDx:

  • Neuroendocrine carcinoma - nucleus often has a plasmacytoid (plasma cell-like) appearance.

Acute myeloid leukemia

General

  • May afflicits young adult.
  • Males>females.

Complications

  • Chloroma - soft tissue mass.
  • Leukostasis.
    • Occurs - lungs and brain.[9]
  • Hyperviscosity syndrome.
  • Spontaneous bleeding with low platelet counts.

Classification

There are two classifications:

  1. FAB (French-American-British) - based on histologic appearance/maturation.
  2. WHO classification.

Histology

Angioimmunoblastic T-cell lymphoma

Microscopic

Features:

  • Clear cytoplasm.
  • "Empty" sinus; subcapsular sinuses "open".

IHC

  • CD7 -ve.
  • CD20 +ve.
  • TIA-1 -ve.

Anaplastic large cell lymphoma

General

  • Abbreviated ALCL.
  • May look a lot like a carcinoma.
    • Often subcapsular in LNs.
  • Usually T-cell derived.
  • Alk IHC:
    • +ve = good prognosis.
    • -ve = bad prognosis.

DDx:

  • Hodgkin's lymphoma.

Microscopic

Features:

  • Large cells with eosinophilic cytoplasm.
  • Usu. appear cohesive.
  • May be subcapsular.
  • Large multinucleated cell - "wreath cell" - key feature.

IHC

Features:

  • Variable CD30 +ve. (???)
  • CD45 +ve. (???)

Table of B-cell lymphoma

Small cell lymphomas:

Name Location Size of cells IHC Translocations Clinical Other
Follicular lymphoma Follicle Small, centrocytes, centroblasts CD10+, bcl-6+[11] t(14,18) Clinical ? Other ?
Mantle cell lymphoma Mantle zone Small CD5+, CD23-, CD43+, cyclin D1+[11] t(11;14)(q13;q32)[12] Clinical ? Other ?
Marginal zone lymphoma (MALT) Marginal zone Small CD21+, CD11c+, CD5-, CD23-[11] Translocations Clinical Other
Precursor lymphoblastic lymphoma/leukemia Location ? Small CD10+, CD5-, TdT+, CD99+[11] Translocations ? Clinical ? Other ?

Medium and large cell lymphomas:

Name Location Size of cells IHC Translocations Clinical Other
Burkitt's lymphoma Follicle Large cells CD10, bcl-6 t(8;14) (q24;q32) Rapid growth "Starry sky"
Diffuse large B cell lymphoma Follicle (?) Large 4-5X of lymphocyte MIB-1 >40% none/like follicular l. Poor prognosis Common among lymphomas
Name Location Size of cells IHC Translocations Clinical Other

Cytometry - population cell marker quantification

Main article: cytometry

Two techniques

  1. Flow cytometry.
  2. Laser scanning cytometry (LSC).

Common markers

  • CD3, CD4, CD8, CD5, CD7.
  • CD19, CD20, FMC7.
  • Kappa, lambda.

Normal

  • T-cells to B-cells usually 1:1.
  • In reactive nodes T-cells predominate.
  • Normal thymic tissue has cells that are positive for both CD4 and CD8.
  • Kappa (k) and lambda (l) are not expressed by the same cell.
  • Rule-of-thumb for normal k:l range is: <6:1 and 1:<3.[13]
    • Lambda dominance is less common.

GS guidelines - non-malignant is:[14]

  • CD19 ~= CD20.
  • CD5 = CD3.
  • CD2 > CD3 and CD5.
  • CD4 + CD8 ~= CD3.
  • CD7 = the smallest number of T-cell.

Abnormal

See cytometry.

See also

References

  1. ↑ http://emedicine.medscape.com/article/1357846-overview
  2. ↑ http://emedicine.medscape.com/article/1357846-diagnosis
  3. ↑ 3.0 3.1 Alanen A, Pira U, Lassila O, Roth J, Franklin RM (March 1985). "Mott cells are plasma cells defective in immunoglobulin secretion". Eur. J. Immunol. 15 (3): 235–42. PMID 3979421.
  4. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 567. ISBN 978-0781765275.
  5. ↑ PMID: 9499174
  6. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 676 (???). ISBN 0-7216-0187-1.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 Bellan C, Lazzi S, De Falco G, Nyongo A, Giordano A, Leoncini L (March 2003). "Burkitt's lymphoma: new insights into molecular pathogenesis". J. Clin. Pathol. 56 (3): 188–92. PMC 1769902. PMID 12610094. http://jcp.bmj.com/cgi/pmidlookup?view=long&pmid=12610094.
  8. ↑ URL: http://www.thefreelibrary.com/Dutcher+bodies+in+chronic+synovitis-a083551789. Accessed on: 4 August 2010.
  9. ↑ AML. Harrison's 16th Ed.
  10. ↑ AG. 8 July, 2009.
  11. ↑ 11.0 11.1 11.2 11.3 Lester, Susan Carole (2005). Manual of Surgical Pathology (2nd ed.). Saunders. pp. 95. ISBN 978-0443066450.
  12. ↑ URL: http://atlasgeneticsoncology.org/Anomalies/t1114ID2021.html. Accessed on: 10 August 2010.
  13. ↑ SB. March 10, 2010.
  14. ↑ GS. LSC Procedure. March 11, 2010.
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