Consensus pathology. (A) Case example of consensus GZL diagnosis (B-cell lymphoma with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma). Sheetlike proliferation of tumor cells resembling PMBL is seen in the top left panel. Focally, collections of eosinophils are noted (top right). The tumor cells are strongly positive for CD20, CD30, and CD15 (bottom). (B) Reclassified case: cHL NS2. Representative images from 2 cases of cHL NS2 are shown. (Top) Characteristic histology with a nodular growth pattern, fibrous bands, and a sheetlike growth of lacunar cells. (Bottom) Immunohistochemical stains from a second case show the nodular growth pattern with strong staining for CD20, but also positivity for CD30 and focal staining for CD15. (C) Reclassified case: primary mediastinal large B cell lymphoma. Diffuse proliferation of large neoplastic cells is seen (top left). The neoplastic cells have abundant clear cytoplasm and vesicular nuclei with basophilic nucleoli (top right). They are strongly, uniformly positive for CD20, with dim expression of CD30, and are negative for CD15 (bottom). (D) Synopsis of the immunohistochemical staining results from consensus confirmed GZL cases. The bar graph illustrates immunohistochemical staining for markers CD20, CD79a, PAX5, MUM1, CD30, CD15, CD3, and in situ hybridization for EBV (EBV-encoded small RNA [EBER]). For immunohistochemical studies, staining was considered to be positive if it had intensity of 2 or more (on +1 to +3 scale) and was distributed in more than 25% of neoplastic cells. Cases with weak/negative expression are not included in this graph. Hematoxylin and eosin staining, original magnification ×400 (A, B [top right panel], and C [top panels]) and ×200 (B [top left panel]). Immunohistochemical staining, original magnification ×400 (all other panels).