Fig. 4.

a–d Session 3, case 01: NLPHL. Lymph node with NLPHL with a characteristic nodular growth pattern (a). LP cells (a, insert) are strongly positive for CD20 and embedded in a background rich in small B cell lymphocytes (b). The LP cells are surrounded by reactive CD57⁺ (c) and PD1⁺ (d) T cells. e–g Session 3, case 03: NLPHL with diffuse areas, depletion of background B lymphocytes and IgD⁺. NLPHL with diffuse growth pattern infiltrating a lymph node (e). Note that the background infiltrate of small B lymphocytes is reduced (f); however, rosetting of PD1⁺ reactive T cells around the LP blasts is present (f, insert). The LP cells are strongly positive for IgD (g). The IgD⁺ LP cells are surrounding the nodules of reactive small B lymphocytes. h–i Session 3, case 09: NLPHL with THRLBCL-like areas. CD20 staining highlights the LP cells with areas of very reduced (h) or complete loss of CD20⁺ small B lymphocytes mimicking THRLBCL (i). j–k Session 3, case 18: NLPHL with CD15 positivity. Typical case of NLPHL with LP cells positive for CD20 (j) showing unequivocal strong expression of CD15 in the LP tumor cells (k). l–n Session 3, cases 07 and 27: NLPHL EBV⁺. CD20 staining highlights the typical characteristics of NLPHL (l) where the LP cells are EBV⁺ by EBER ISH (m). Case 27 showed in addition progression to a DLBCL. Note that the high-grade component (left), as well as the LP cells (right) are EBER⁺ (s)