Angioimmunoblastic T-cell lymphoma

CLINICAL FEATURES

• A peripheral T-cell lymphoma with a polymorphous infiltrate in lymph node, a prominent proliferation of high endothelial venules and follicular dendritic cells;

• Age: middle to elderly; Gender: M=F;

• 15-20% of peripheral T-cell lymphoma, 1-2% of non-Hodgkin lymphoma;

• Clinical presentations: often generalized peripheral lymphadenopathy, hepatosplenomegaly, frequent skin rash, and commonly bone marrow involvement upon biopsy.

MICROSCOPIC FINDINGS

• Loss of normal lymph node architecture
  • Diffuse paracortical infiltrate of polymorphous neoplastic T cells
  • Lymph node architecture is partially or totally effaced
  • Lymphoid follicles, hyperplastic, depleted or regressed, with irregular borders and lack of mantle zones
• Neoplastic T cells
  • Small to medium-sized but occasionally large cells, usually show minimal cytologic atypia
  • Abundant clear to pale cytoplasm, distinct cell membranes and irregular nuclear contour
  • Often in clusters around high endothelial venules
  • Often obscured by reactive lymphocytes, immunoblasts, plasma cells, histiocytes, and eosinophils
• Prominent proliferation high endothelial venules
  • Prominent arborizing high endothelial venules with PAS positive amorphous perivascular material
  • The nuclei of endothelial cells are round to oval with regular nuclear contour and a small central nucleolus
• Prominent proliferation of follicular dendritic cells
  • Follicular dendritic cell proliferation outside germinal centers/around high endothelial venules
  • Highlighted by CD21 staining
• B cell proliferation
  • >70% are EBV positive
  • May be polymorphic or monomorphic, immunoblastic or plasmacytic
  • Immunoglobulin gene rearrangement detected in 10% cases
  • May produce a Hodgkin-like proliferation with Reed-Sternberg-like cells

DIFFERENTIAL DIAGNOSES

• Reactive lymphadenopathies

• Multicentric Castleman's disease

• Diffuse large B-cell lymphoma

• Classical Hodgkin's Disease

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

• Neoplastic cells are mature T-cells with CD3+, CD4+

• In most cases, the neoplastic T-cells show aberrant expression of CD10

• Loss of T-cell antigen such as CD7 can occur in some cases

• EBV positive in >75% cases, mostly in B-cells, not T-cells

• Follicular dendritic cells CD21+

• •TCR gene rearrangement in 75% cases
• 90% have cytogenetic alterations: trisomy 3, trisomy 5 and gain of chromosome X

TREATMENT AND PROGNOSIS

• Aggressive, median survival <3 years

REFERENCES

• Jaffe ES, Harris NL, Stein H, Vardiman JW, editors. Pathology and genetics of tumours of haematopoietic and lymphoid tissues. World Health Organization classification of tumours. Lyon (France): IARC Press; 2001.

• Practical Diagnosis of Hematologic Disorders, Fourth Edition. By Carl R. Kjeldsberg, 2006.