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5. Tumours of Mature Peripheral T-cells

• 5.1 Angioimmunoblastic T-cell Lymphoma
• 5.2 Anaplastic Large Cell Lymphoma - T-cell Type
• 5.3 Peripheral T-cell Lymphoma, Common (Unspecified)
• 5.4 Extranodal NK/T-cell Lymphoma, nasal type
• 5.5 Enteropathy Type T-cell Lymphoma

T-cell or NK-cell lymphocytosis - summary reference table

5.1 Angioimmunoblastic T-cell Lymphoma

This is a peripheral T-cell lymphoma associated with a distinctive syndrome of systemic effects.

Diagnostic Criteria

1. Loss of nodal architecture with proliferation of high endothelial cells, follicular dendritic cells, reactive T and B-cells and plasma cells
2. Neoplastic population consists of intermediate sized T-cells with clear cytoplasm. CD4⁺ T-cells which may express CD10
3. Clonal TCR rearrangement demonstrated by PCR. If neither a TCRβ or a TCRγ rearrangement is demonstrated the case should be reviewed and presented at MDT.
4. Systemic features including rashes, pleural effusions, fever, hypergammaglobulinaemia and Coombs positive haemolytic anaemia

Term to be Used

5.2 Anaplastic T-cell Lymphoma

This group of peripheral T-cell lymphomas is defined by anaplastic morphology and expression of CD30.

Diagnostic Criteria

Typical Cases

1. Anaplastic large lymphoid cells some of which have horseshoe shaped nuclei and eosinophilic paranuclear cytoplasm
2. Immunophenotype: CD30⁺,CD45⁺,CD15^- with variable expression of T-cell markers
3. Sometimes sinusoidal or perivascular pattern of infiltration is present
4. Clonal TCR rearrangement. If neither a TCRβ or a TCRγ rearrangement is demonstrated the case should be reviewed and presented at MDT.

Variants

1. Morphological variants include small cell and lymphohistiocytic types

Prognostic factors

1. Alk rearrangement implies a favourable prognosis and is more common in younger patients. Typical translocations show nuclear and cytoplasmic Alk expression. Variant translocations show only cytoplasmic Alk

Term to be used

5.3 Peripheral T-cell Lymphoma, Common (Unspecified)

This term is used for all other types of peripheral T-cell lymphoma.

Diagnostic Criteria

1. Tumour deposit, nodal replacement by cytologically abnormal T-cells
2. Peripheral T-cell phenotype. This will almost always be abnormal
3. Does not meet specific criteria for angioimmunoblastic or anaplastic large cell types
4. Clonal TCR rearrangement. If neither a TCRβ or a TCRγ rearrangement is demonstrated the case should be reviewed and presented at MDT.
5. High WBC in peripheral blood specimens
6. Pleomorphic lymphocyte morphology
7. Phenotypically characterised by loss of one or more pan-T cell antigens (CD2, CD3, CD5 or CD7). Can be CD4⁺ or CD8⁺
8. Express activation antigens CD25, HLA-DR, CD45R0, CD56

Differential diagnosis

Other well characterised T-LPD's and T-ALL must be excluded. Care should be taken in diagnosing peripheral T cell lymphoma (unspecified) in PB or bone marrow samples. If the patient has nodal or extranodal disease a biopsy should be performed.

Term to be used

5.4 Extranodal NK/T-cell Lymphoma, nasal type

This is a rare form of aggressive lymphoma typically affecting the nose but also affecting other extranodal sites including skin and GI tract. The tumour has an NK cell phenotype.

Diagnostic Criteria

1. Highly pleomorphic lymphoid infiltrate.
2. Almost all cases have necrosis and vascular desctruction.
3. Immunophenotype: CD2⁺,CD5^-, CD56⁺,CD57^-,GranB⁺
4. Germline TCRγ
5. The incidence of EBV association is not well described

Variant:

Clinically identical tumours with a cytotoxic T-cell Phenotype are described

Term to be used

5.5 Enteropathy Type T-cell Lymphoma

This is a specific type of peripheral T-cell lymphoma associated with enteropathy/coeliac disease.

Diagnostic Criteria

Typical Cases

1. History of coeliac disease or morphological evidence of enteropathy
2. Ulcer, perforation or mass in small intestine
3. Infiltrate of large lymphoid cells
4. Immunophenotype: CD3⁺,CD4^-,CD5^-,CD7^+/-,CD8^-,CD56^+/-,CD30^+/-
5. Clonal T-cell rearrangement by PCR. If neither a TCRβ or a TCRγ rearrangement is demonstrated the case should be reviewed and presented at MDT.

Variant

1. Intramucosal Type
   • History of refractory coeliac/jejunal ulceration
   • Intra-epithelial lymphocytes show cytological atypia
   • Intra-epithelial lymphocytes CD8^-,CD4^-,CD56^+/-
   • Clonal TCR rearrangement

All these diagnostic criteria must be present

Terms to be Used

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