Pathological features of pyloric gland adenoma of the gallbladder in comparison with gastric subtype of intracholecystic papillary neoplasm

Genomic and transcriptomic signatures of sequential carcinogenesis from papillary neoplasm to biliary tract cancer

BACKGROUND & AIMS

Papillary neoplasms of the biliary tree, including intraductal papillary neoplasms (IPNs) and intracholecystic papillary neoplasms (ICPNs), are recognized as precancerous lesions. However, the genetic characteristics underlying sequential carcinogenesis remain unclear.

METHODS

Whole-exome sequencing was performed on 166 neoplasms (33 intrahepatic IPNs, 44 extrahepatic IPNs, and 89 ICPNs), and 41 associated carcinomas. Nine available cases were also subjected to spatial transcriptomic analysis.

RESULTS

Mutations in the MAPK (48%), genomic integrity maintenance (42%), and Wnt/β-catenin (33%) pathways were prevalent in intrahepatic IPNs, extrahepatic IPNs, and ICPNs, respectively. KRAS mutations were enriched in intrahepatic IPNs (42%, p <0.001), whereas SMAD4 mutations were enriched in extrahepatic IPNs (21%, p = 0.005). ICPNs frequently exhibit CTNNB1 mutations, particularly in low-grade lesions. Mutational signature analysis revealed that SBS1 and SBS5 signatures were homogeneously enriched in intrahepatic IPNs, in contrast to the heterogeneous distribution of SBS1, SBS2, SBS5, SBS13, SBS7b, and SBS23 in extrahepatic IPNs and ICPNs. Copy number aberrations gradually increased from low-to high-grade intraepithelial neoplasia and eventually to carcinoma. Phylogenetic analysis revealed that 89% of carcinomas were derived from IPNs/ICPNs through sequential carcinogenesis, with the majority sharing driver mutations between the IPN/ICPN and the carcinoma. Furthermore, multifocal, independent carcinogenesis events were observed in IPNs/ICPNs, resulting in mutationally distinct carcinoma lesions. Carcinogenesis of IPN/ICPN occurs in multiple subclones through mutational accumulation and transcriptomic alterations that affect vascular development, cell morphogenesis, extracellular matrix organization, and growth factor response.

CONCLUSIONS

With the largest IPN/ICPN cohort reported to date, our study provides a genome- and spatial transcriptome-level portrait of sequential carcinogenesis and differences in the anatomical location of biliary papillary neoplasms.

IMPACT AND IMPLICATIONS

Biliary tract cancer is a fatal malignancy. However, the genome-level sequential progression from intraepithelial neoplasia to carcinoma has not yet been evaluated in a sufficiently large cohort. Papillary lesions of the bile duct and gallbladder are collectively termed intraductal papillary neoplasms of the bile duct and intracholecystic papillary neoplasms, respectively. They are primarily diagnosed based on histopathological studies. This study provides a comprehensive mutational and spatial transcriptomic landscape of papillary neoplasms of the bile duct and gallbladder. The results of this study offer insights into the mechanism of sequential carcinogenesis in papillary biliary tract tumors, pathology-genomic correlations, and potential therapeutic targets.

Detached pyloric gland adenoma of gallbladder: A case report and review of literature

Key Clinical Message

Vigilant intraoperative inspection is crucial during gallbladder surgery to detect any abnormal tissue including the rare pyloric gland adenomas, which can be easily missed. Thorough examination and removal of unusual lymph nodes or thickened tissues are essential to prevent the risk of malignant transformation and ensure comprehensive patient care.

Abstract

Pyloric gland adenomas are uncommon tumors that can be discovered in various organs such as the stomach, gallbladder, and pancreas. Typically lacking noticeable symptoms, these tumors are categorized into subtypes, with the pyloric variant being the most frequent. The term "intracholecystic papillary-tubular neoplasms (ICPN)" is used to emphasize growth patterns and associated risks. In a discussed case, a detached pyloric gland adenoma was identified incidentally during a cholecystectomy procedure. A 58-year-old obese male presented with upper abdominal pain, nausea, and vomiting. He was diagnosed with early cholecystitis caused by gallstones. Subsequently, during a laparoscopic cholecystectomy, a detached adenoma was discovered. Vigilant screening is crucial, as the identification of gallbladder pyloric gland adenomas is a rare occurrence that might be missed during gallbladder surgery. Any unusual lymph nodes or thickened tissues found in association with the gallbladder ought to be carefully removed, as they could potentially indicate detached gallbladder adenomas with a significant risk of becoming malignant. Failing to consider this possibility may subject the patient to prolonged risks if not meticulously examined.

Pathologic significance of peribiliary capillary plexus in gallbladder neoplasm

AIMS

Significance of peribiliary capillary plexus (PCP) in gallbladder neoplasms remains unclear. Aims are to characterize high-grade biliary intraepithelial neoplasm (BilIN), pyloric gland adenoma (PGA), and intracholecystic papillary neoplasm (ICPN), precursors of gallbladder carcinoma, and to differentiate invasive carcinoma from pseudo-invasive lesions in gallbladder walls, referring to PCP.

MATERIALS AND METHODS

High-grade BilIN (38 cases), PGA (5 cases), and ICPN (25 cases) were examined using capillary immunostaining. Non-neoplastic gallbladders were used as controls.

RESULTS

In non-neoplastic gallbladders, a single layer of regularly dotted capillaries (PCP) was located beneath lining epithelia and around non-neoplastic glands (NNGs), including Rokitansky-Aschoff sinus (RAS), presenting a two-layer of lining epithelia and PCP. Intra-luminal components of all cases of high-grade BilIN and PGA and one-third of ICPNs presented a two-layer pattern. In the remaining ICPNs, capillaries were irregular and sparse in intraluminal neoplastic components presenting irregular and complicated lesions. Neoplastic glands in gallbladder walls of high-grade BilIN and ICPN were classifiable into 2 types: glands that were underlain by densely dotted capillaries and those that were not, with the latter suggestive of invasive carcinoma, while the former suggestive of non-invasive neoplasms involving NNGs intraepithelially and/or showing an expanding growth into gallbladder wall (pseudo-invasion).

CONCLUSION

A two-layer pattern of lining epithelia and underlining capillaries were preserved in all cases of high-grade BilIN and PGA and one-third of ICPN cases. Presence or absence of dotted capillaries around neoplastic glands may be able to be added as a new pathologic feature to differentiate invasive carcinomas from pseudo-invasion in gallbladder wall.

Dysplasia and Early Carcinoma of the Gallbladder and Bile Ducts: Terminology, Classification, and Significance

Most precursor lesions and early cancerous changes in the gallbladder and bile ducts present as clinically/grossly inapparent lesions. Low-grade dysplasia is difficult to define and clinically inconsequential by itself; however, extra sampling is required to exclude accompanying significant lesions. For high-grade dysplasia ('carcinoma in situ'), a complete sampling is necessary to rule out invasion. Tumoral intramucosal neoplasms (ie, intracholecystic and intraductal neoplasia) form radiologically/grossly visible masses, and they account for (present in the background of) about 5% to 10% of invasive cancers of the region. These reveal a spectrum of papilla/tubule formation, cell lineages, and dysplastic transformation. Some subtypes such as intracholecystic tubular non-mucinous neoplasm of the gallbladder (almost never invasive) and intraductal oncocytic or intraductal tubulopapillary neoplasms of the bile ducts (may have a protracted clinical course even when invasive) are to be noted separately. Other types of intracholecystic/intraductal neoplasia have a high frequency of invasive carcinoma and progressive behavior, which often culminates in mortality.