Intertumoral heterogeneity represents a significant hurdle to identifying optimized targeted therapies in gastric cancer (GC). To realize precision medicine for GC patients, an actionable gene alteration-based molecular classification that directly associates GCs with targeted therapies is needed. A total of 207 Japanese patients with GC were included in this study. Formalin-fixed, paraffin-embedded (FFPE) tumor tissues were obtained from surgical or biopsy specimens and were subjected to DNA extraction. We generated comprehensive genomic profiling data using a 435-gene panel including 69 actionable genes paired with US Food and Drug Administration-approved targeted therapies, and the evaluation of Epstein-Barr virus (EBV) infection and microsatellite instability (MSI) status. Comprehensive genomic sequencing detected at least one alteration of 435 cancer-related genes in 194 GCs (93.7%) and of 69 actionable genes in 141 GCs (68.1%). We classified the 207 GCs into four The Cancer Genome Atlas (TCGA) subtypes using the genomic profiling data; EBV (N = 9), MSI (N = 17), chromosomal instability (N = 119), and genomically stable subtype (N = 62). Actionable gene alterations were not specific and were widely observed throughout all TCGA subtypes. To discover a novel classification which more precisely selects candidates for targeted therapies, 207 GCs were classified using hypermutated phenotype and the mutation profile of 69 actionable genes. We identified a hypermutated group (N = 32), while the others (N = 175) were sub-divided into six clusters including five with actionable gene alterations: ERBB2 (N = 25), CDKN2A, and CDKN2B (N = 10), KRAS (N = 10), BRCA2 (N = 9), and ATM cluster (N = 12). The clinical utility of this classification was demonstrated by a case of unresectable GC with a remarkable response to anti-HER2 therapy in the ERBB2 cluster. This actionable gene-based classification creates a framework for further studies for realizing precision medicine in GC.

Assessment of lymph node status is a critical issue in the surgical management of gallbladder cancer. The aim of this study was to compare the anatomical location of positive nodes, number of positive nodes, and lymph node ratio (LNR) as prognostic predictors in gallbladder cancer.

Inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn’s disease (CD), is a chronic, idiopathic, repeated inflammatory disease. Colorectal cancer (CRC) that develops in patients with IBD is known as colitis-associated colorectal cancer (CAC), but the underlying carcinogenic mechanism remains unclear. Genomic analysis of sporadic CRC has been well described based on next-generation sequencing (NGS) data. Using NGS, we compared all exons of 415 cancer-associated genes in patients in Japan and the USA who had CRC and found similar genomic alteration patterns among the two populations. However, genomic analysis of CAC has not been thoroughly investigated. The molecular pathogenesis of CAC shares many features with sporadic CRC, but there are distinct variations in the time and frequency of some alterations. Gene alterations in CAC are gradually being elucidated using genomic sequencing analyses. Some studies have shown that gene alteration patterns differ between UC and CD. The carcinogenesis of CAC depends on unique environmental, genetic, and immunological factors. In this review, we have discussed the differences in genomic alterations between sporadic CRC and CAC. NGS in patients with IBD has the potential to detect early CAC and to suggest therapeutic targets.

Recent advances in dimensional imaging, surgical technique, and perioperative patient care have resulted in increased rates of complete resection with histopathologically negative margins and improved surgical outcomes in patients with extrahepatic cholangiocarcinoma. However, achieving cancer‐free resection margins at ductal stumps in surgery for this disease remains challenging because of longitudinal extension, which is one of the hallmarks of extrahepatic cholangiocarcinoma. When the ductal resection margins are shown to be positive on examination of frozen sections, discrimination between carcinoma in situ and invasive carcinoma is clinically important because residual carcinoma in situ may lead to late local recurrence whereas residual invasive carcinoma is associated with early local recurrence. Residual invasive carcinoma at the ductal margins should be avoided whenever technically feasible. Residual “carcinoma in situ” at the ductal margins appears to be allowed in resection for the advanced disease because it has less effect on survival than other adverse prognostic factors (pN1 and/ or pM1). However, in surgery for early‐stage (pTis‐2N0M0) extrahepatic cholangiocarcinoma, residual carcinoma in situ at the ductal margins may have an adverse effect on long‐term survival, so should be avoided whenever possible. In this review, we focus on the histopathological term “carcinoma in situ,” the biological behavior of residual carcinoma in situ at ductal resection margins, intraoperative histological examination of the ductal resection margins, outcome of additional resection for positive ductal margins, and adjuvant therapy for patients with positive margins.