Two Gastric Cancers with Uncommon ALK Fusion Diagnosed with Comprehensive Panel Sequencing and Confirmed with Companion Diagnostic Assay

ALK gene rearrangement is clinically significant due to the ALK tyrosine kinase inhibitor, important in several types of ALK-rearranged malignancies, most prominently in non–small cell lung cancers. ALK fusion in the gastrointestinal tract is rare. Herein, we report 2 cases of gastric cancer, in which ALK is fused with two uncommon partners, SLMAP and STRN. Two cases of ALK fusion were identified by comprehensive panel sequencing of 231 clinical gastric cancer samples. The results were confirmed using the Ventana ALK (D5F3) CDx assay. Both were advanced stage and were signet ring cell carcinomas with histological features comparable to those of ALK-rearranged non–small cell lung cancers. The patients were treated with conventional chemotherapy ALK fusion, one of the druggable targets in other solid tumors, is rare in gastric cancers and can be detected by comprehensive panel sequencing. Clinical studies are warranted to investigate the therapeutic response of ALK inhibitors in gastric cancers with ALK fusion.