Fig. 4.

Structural organization and in silico modeling of canonical and noncanonical STRN::ALK fusion variants identified in oncocytic thyroid tumors (a) Schematic representation of canonical and noncanonical STRN::ALK fusion architectures detected in this study. The canonical variant corresponds to the expected in-frame STRN exon 3-ALK exon 20 fusion, preserving the ALK kinase domain. Noncanonical variants include structurally altered out-of-frame transcripts characterized by internal deletions and/or premature stop codons predicted to disrupt preservation of kinase-domain features (b) In silico structural modeling of representative canonical and noncanonical fusion products. Canonical fusions retained overall structural organization consistent with preservation of ALK kinase-domain features, whereas noncanonical variants demonstrated partial structural disruption (Type I) or severe truncation with absence of recognizable kinase-domain organization (Type II). Structural models are displayed at proportional relative scale to illustrate the predicted truncation of noncanonical variants