Follicular Peripheral T-cell Lymphoma
There is a variant of peripheral T-cell lymphoma (PTCL) with a predominantly follicular or perifollicular growth pattern that shows some overlap with angioimmunoblastic T-cell lymphoma (AITL). It arises from follicular helper T-cells (like AITL) but does not show the polymorphic infiltrate or the vascular overgrowth (high endothelial venules) of AITL. About 20% of patients with follicular PTCL carry a chromosomal translocation t(5;9)(q33;q22) involving ITK and SYK tyrosine kinase genes. This translocation, which results in ITK-SYK fusion transcript, has also been reported in some cases of typical AITL. Follicular T-cell lymphomas express BCL6 more frequently than AITL. This low power view of a follicular PTCL shows vaguely nodular growth pattern.