Growth patterns in the cases classified as LPHD.

(A) In most cases, a nodular growth pattern was conceivable at low power (H&E-stained). (B) and (C) Immunostains for CD20 disclosed that the nodules in nodular LPHD usually consisted of accumulations of small B cells (B). Occasionally, nodules rich in T cells were encountered admixed with B-cell rich ones (C). (D) Immunostains for CD20 proved useful also in detecting residual nodular structures in LPHD cases with predominantly diffuse growth pattern. (E) and (F) Labeling for CD21 (using the monoclonal anti-CD21 antibody 1F8 and the APAAP method) illustrated the presence of a follicular dendritic cell meshwork within the LPHD nodules, which engulfed the neoplastic cells with their rosettes (F). (G) and (H) Within the LPHD nodules, a varying number of CD57⁺ T cells was found (G). These cells often formed rosettes around the neoplastic cells as shown at higher magnification (H). (Immunostains using the anti-CD57 monoclonal antibody Leu7 and the APAAP technique).