16. Follicular lymphoma

Staining: HE

Organ: Lymph node with perinodal fat

Description:

Abnormal follicles are visible. These follicles are made up of tumor cells and are therefore called neoplastic follicles. The tumor cells show only mild atypia/pleiomorphism. The neoplastic follicles have broken mantle zone and shows no “starry sky” pattern. The neoplastic follicles infiltrate the perinodal fat tissue.

The tissue between the neoplastic follicles appears compressed.

Diagnosis: Follicular lymphoma

Causes:

• t(14;18) translocation – fusion of BCL2 and IgH genes

Theory:

The translocation of the IgH gene (with its highly active promoter region) into the BCL2 (an antiapoptotic protein) on chromosome 18 causes the BCL2 gene to be overexpressed. These cells therefore have high antiapoptotic activity. Due to this is there no apoptosis in the follicles, so the “starry sky” pattern not visible.

Overview

No starry sky pattern. The mantle zone (the ring of darker stained cells) is incomplete as it is broken on the bottom aspect.

Left: Physiological follicular hyperplasia. Right: Follicular lymphoma. The two different slides are not at the same magnification. Note how the follicles in follicular lymphoma have less prominent and more incomplete mantle zones. Also, even at this magnification can you see the absence of “starry sky” pattern on the right picture.

The area between the neoplastic follicles is compressed

The tumor cells show only mild atypia/pleomorphism. This is taken from a neoplastic follicle.