Haematopathology

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.

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.

Lymphoma

Main article: Lymphoma

Plasma cell lesions

See the lymphoma article.

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.
  • Lambda dominance is less common.

GS guidelines - non-malignant is:

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

Abnormal

See cytometry.

See also

• Stomach.
• Lymph nodes.