ALK-Negative Anaplastic Large Cell Lymphoma (ALCL): Prognostic Implications of Molecular Subtyping and JAK-STAT Pathway

The anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) is a clinically distinct but heterogeneous entity and lacks the specific immunophenotypic or genetic features compared with the ALK-positive ALCL. Recent molecular studies have provided genetic landscapes of ALK-negative ALCL that have prognostic significance. In this study, we subtyped ALK-negative ALCL based on DUSP22 rearrangements and TP63 expression and also looked for mutations in JAK-STAT pathway. The subtyping of the ALK-negative ALCL in relation to DUSP22 rearrangement and TP63 expression was done using fluorescence in situ hybridization and immunohistochemistry, respectively. The hotspot JAK-STAT mutations were analyzed using Sanger sequencing and amplification refractory mutation system polymerase chain reaction (PCR) and Signal transducer and activator of transcription 3 (STAT3) expression by immunohistochemistry. Forty-eight cases of ALCL were included with median age of 30 years and sex ratio of 1.8:1. The p63 expression was detected in 26.7% of ALK-negative ALCL cases. DUSP22 rearrangement was noted in 12.5% cases of p63-negative ALK-negative ALCLs. DUSP22 rearranged cases had better overall survival in contrast to p63 expressing and triple negative ALCLs. Triple negative ALCLs showed inferior overall survival rate. STAT3 expression was evident in 61.1% and 60% of ALK-positive and ALK-negative ALCLs, respectively. None of the cases subjected to Sanger sequencing as well as amplification refractory mutation system PCR for hotspot mutation analysis of JAK1 (exon 24) and STAT3 (exon 21) revealed any mutation. ALK-negative ALCL is a genetically heterogeneous disease with widely disparate clinical outcomes. Subtyping of ALK-negative ALCL based on DUSP22 rearrangement and p63 expression provides prognostic information.