JAK/STAT3 Signaling Activation Related to Distinct Clinicopathologic Features in Systemic ALK- Anaplastic Large Cell Lymphomas New Insights into Their Heterogeneity

Systemic anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) is a group of heterogenous CD30(+) T-cell non-Hodgkin lymphomas. Previous studies have highlighted the importance of JAK/STAT3 signaling activation in the molecular pathogenesis of ALK(-) ALCLs. In the present study, we aimed to establish a potential relationship between JAK/STAT3 signaling activation and clinicopathologic features in ALK(-) ALCLs, and further recognize the heterogenous nature of these neoplasms. Immunohistochemistry staining of the phosphorylated-STAT3 (p-STAT3) and dual-specificity protein phosphatase 22 (DUSP22) gene rearrangement analysis were performed. Forty-five cases of ALK(-) ALCL were divided into 3 groups, including 9 DUSP22-rearranged ALCLs, 21 p-STAT3(+) double-negative (DN) ALCLs (both ALK and DUSP22 rearrangement negative), and 15 p-STAT3(-) DN-ALCLs. Morphologically, p-STAT3(+) DN-ALCLs exhibited sheet-like neoplastic cells and sometimes showed large pleomorphic cells scattered in a lymphocyte-rich background more frequently than those in other ALK(-) ALCLs subtypes. Phenotypically, the p-STAT3(+) DN-ALCLs frequently expressed cytotoxic molecules, epithelial membrane antigen, and programmed death-ligand 1, whereas CD3 and CD5 expression was not observed. Clinically, patients with p-STAT3(+) DN-ALCLs had a better prognosis than those with p-STAT3(-) DN-ALCLs. These observations suggest that p-STAT3(+) DN-ALCLs represent a distinct subtype of ALK(-) ALCLs. Identifying ALK(-) ALCL subtypes by using p-STAT3 staining and DUSP22 rearrangement is a promising approach that may contribute to risk stratification and better treatment decisions in the future clinical practice.