STAT6 and phosphorylated STAT6 are differentially expressed in lymphomas

Background: The STAT6 pathway is implicated in the pathogenesis of various lymphomas; however, its immunohistochemical expression has not been fully investigated. Thus, the aim of this study was to investigate the immunohistochemical expression of the two forms of STAT6, phosphorylated or not, in a series of systemic lymphomas. Materials and methods: Immunohistochemical expression of two antibodies, STAT6 (clone YE361) and pSTAT6 (clone Y641), which recognise the phosphorylated form of the molecule was studied in 60 lymphomas. Results: STAT6(YE361) expression was cytoplasmic, with 23.3% of the cases showing high expression. pSTAT6(Y641) expression was mostly nuclear and found in 45% of the cases. pSTAT6(Y641) nuclear expression was associated with the lymphoma type (p < 0.0001), as it was seen mostly in follicular, Hodgkin and angioimmunoblastic T cell lymphomas. STAT6(YE361) cytoplasmic expression was also associated with lymphoma type (p = 0.001), as it was mostly found in diffuse large B cell and marginal B cell lymphomas. No association with PD-L1 expression, other clinicopathological data or prognosis was found. Conclusion: The two STAT6 clones are differentially expressed between lymphoma types.