Follicular hyperplasia, follicular lysis, and progressive transformation of germinal centers. A sequential spectrum of morphologic evolution in lymphoid hyperplasia.

We studied mantle B-cell and T-cell ingression in hyperplastic follicles (HFs), follicular lysis (FL), and progressive transformation of germinal centers (PTGC) in 19 paraffin-embedded, H&E-, bcl-2-, CD20-, and CD3-stained lymph nodes. We enumerated the T cells (CD3+) and mantle B cells (bcl-2+/CD3-) per 100 cells in 5 high-power fields of each entity (mean +/- SD). Compared with HF, FL had increased numbers of T cells migrating into germinal centers (39.8 +/- 10.0 vs 25.8 +/- 7.8; P < .0001). and a mild increase of mantle B cells (12.3 +/- 11.4 vs 2.1 +/- 1.6; P < .001). PTGC showed an increase of T-cell ingression compared with HF (36.5 +/- 12.1 vs 25.8 +/- 7.8; P < .0001) and more migration of mantle B cells into the follicle than FL (41.0 +/- 22.5 vs 12.3 +/- 11.4; P < .0001). T cells and mantle B cells ingress in FL and PTGC, although the mantle B-cell component predominates in the latter, suggesting that follicular hyperplasia, FL, and PTGC constitute an evolutionary spectrum in resolution of lymphoid hyperplasia with sequential ingression of T cells followed by mantle B cells. The maintenance of bcl-2 expression in mantle B cells in PTGC may cause differential diagnostic pitfalls in florid PTGC vs follicular lymphoma, particularly the so-called floral variant.