Immunolabeling for B-cell–associated signaling molecules in lymphocyte predominance Hodgkin disease. All staining was performed on paraffin biopsies by immunoperoxidase or double immunofluorescent techniques. (A) Left: Two cases of lymphocyte predominance Hodgkin disease (nos. 4 and 7 in Table 1), showing Lyn-negative (white arrows) and Lyn-positive (black arrows) L&H cells. Right: Double immunofluorescent staining of another case (no. 6 in Table 1) shows an L&H cell (white arrow) that is CD79a positive but Lyn negative. (B) Left: Many L&H cells are Fyn positive (black arrows) in a case of lymphocyte predominance Hodgkin disease (no. 14 in Table 1) as seen at higher magnification in the insets. Right: Double immunofluorescent staining for CD20 (red) and Fyn (green) confirms coexpression of these markers in L&H cells (white arrows). The numerous mantle zone B cells in this field are also strongly CD20/Fyn positive. (C) Left: Strong reactivity of L&H cells (black arrows) for Syk, as seen at higher magnification in the insets. Right: Double immunofluorescent labeling confirms the coexpression of CD20 (green, membrane associated) and Syk (red, cytoplasmic) in L&H cells (white arrows). (D) Left: Numerous strongly BLNK-positive L&H cells (black arrows), seen at higher magnification in the insets, lie within nodules of BLNK-positive B cells. Right: Double immunofluorescence for CD79a (red) and BLNK (green) confirms coexpression of these markers in L&H cells (white arrows and inset). (E) Left: L&H cells are strongly PLC-γ2 positive (as seen at higher power in the inset). Right: Double immunofluorescence shows coexpression of CD20 (green, membrane associated) and PLC-γ2 (red, intracellular) in L&H cells (arrows). Original magnifications: × 20 (A-D, E left panel), × 40 (A-E insets, E right panel).