Expression of phosphorylated STAT proteins in malignant lymphomas.

Expression of P-STAT6 (A-E), P-STAT3 (F-I), and P-STAT5 (J-O) was examined by immunohistochemistry in formalin-fixed sections of classical HL (cHL), nLPHL, ALCL, and DLBCL. Staining for nuclear P-STAT6 was positive in HRS cells of cHL (A). In nLPHL, lymphocytic and histiocytic cells were P-STAT6⁻, whereas scattered macrophage nuclei were P-STAT6⁺ (B). P-STAT6 was also positive in 33% cases of ALCL (C-D), and negative in DLBCL (E). Nuclear P-STAT3 was present in HRS cells and cells in the reactive infiltrate in cHL (F), lymphocytic and histiocytic cells and cells in the reactive infiltrate from nLPHL (G), ALCL (H), and DLBCL (I). Nuclear P-STAT5 was present in HRS cells in 26% of cHL (J-K), negative in lymphocytic and histiocytic cells in nLPHL (L), positive in 50% of ALCL (M-N), and negative in DLBCL (O). Original magnifications, × 720.