Expression profiles of gastric cancer molecular subtypes in remnant tumors

BACKGROUND Remnant gastric cancer (RGC) is a carcinoma arising in the stomach remnant after previous gastric resection. It is frequently reported as a tumor with a poor prognosis and distinct biological features from primary gastric cancer (PGC). However, as it is less frequent, its profile regarding the current molecular classifications of gastric cancer has not been evaluated. AIM To evaluate a cohort of RGC according to molecular subtypes of GC using a panel of immunohistochemistry and in situ hybridization to determine whether the expression profile is different between PGC and RGC. METHODS Consecutive RGC patients who underwent gastrectomy between 2009 and 2019 were assessed using seven GC panels: Epstein-Barr virus in situ hybridization, immunohistochemistry for mismatch repair proteins (MutL homolog 1, MutS homolog 2, MutS homolog 6, and PMS1 homolog 2), p53 protein, and E-cadherin expression. Clinicopathological characteristics and survival of these patients were compared to 284 PGC patients. RESULTS A total of 40 RGC patients were enrolled in this study. Compared to PGC, older age (P < 0.001), male (P < 0.001), lower body mass index (P = 0.010), and lower hemoglobin level (P < 0.001) were associated with RGC patients. No difference was observed regarding Lauren's type and pathologic Tumor Node Metastasis stage between the groups. Regarding the profiles evaluated, EBV-positive tumors were higher in RGC compared to PGC (P = 0.039). The frequency of microsatellite instability, aberrant p53 immunostaining, and loss of E-cadherin expression were similar between RGC and PGC. Higher rates of simultaneous alterations in two or more profiles were observed in RGC compared to PGC (P < 0.001). According to the molecular classification, the subtypes were defined as EBV in nine (22.5%) cases, microsatellite instability in nine (22.5%) cases, genomically stable in one (2.5%) case, and chromosomal instability in 21 (52.5%) cases. There was no significant difference in survival between molecular subtypes in RGC patients. CONCLUSION RGC was associated with EBV positivity and higher rates of co-altered expression profiles compared to PGC. According to the molecular classification, there was no significant difference in survival between the subtypes of RGC.