Follicular Lymphoma : Diffuse areas

Comments:
A diffuse area in a follicular lymphoma (FL) lacks identifiable neoplastic follicles but is composed of the same admixture of neoplastic cells as those seen in the neoplastic follicles. The image shows an area where the follicular pattern is becoming indistinct and is being replaced by diffuse areas.

In grade 1-2 follicular lymphomas, the WHO Classification addresses the diffuse areas as follows: follicular (>75% follicular), follicular and diffuse (25% to 75% follicular), predominantly diffuse (<25% follicular), and diffuse (0% follicular).

Diffuse areas in low-grade FL do not appear to impact the prognosis. However, a diffuse lymphoma with a predominance of centroblasts (>15 centroblasts/hpf; grade 3) should be diagnosed as diffuse large B-cell lymphoma and has a worse prognosis.