Abstract
Scirrhous-type gastric cancer (SGC) is a rare but well-recognized subset of resectable gastric cancer (GC), accounting for ⁓10% of cases. Despite its long history of clinical recognition dating back to the pre-1900s, SGC remains one of the most challenging GC subtypes to treat. Traditionally, SGC has been clinically defined as Borrmann type 4 GC, with histological classifications such as signet ring cell carcinoma or diffuse-type histology serving as alternative diagnostic criteria. Therapeutic advancements for SGC have largely focused on locally advanced or oligometastatic disease, yet no SGC-specific treatment has been established. The phase III JCOG0501 trial failed to demonstrate a survival benefit of neoadjuvant S-1 plus cisplatin for Borrmann type 4 and large type 3 GC. Recent developments in biomarker-driven therapies may redefine SGC by molecular subtypes, with CLDN18.2-targeted therapy emerging as a potential option for some SGC cases. However, as the landscape of medical oncology evolves, SGC may not remain a distinct therapeutic entity. The focus should shift toward understanding the intrinsic biology of SGC. Treatment development for SGC is expected to continue advancing, becoming increasingly stratified based on molecular abnormalities while maintaining a commitment to addressing unmet needs, such as early-onset GC and GC with symptomatic peritoneal dissemination.