Colorectal serrated adenocarcinoma

Area of Science:

• Oncology
• Gastroenterology
• Molecular Pathology

Background:

• Colorectal cancer (CRC) is a leading cause of cancer incidence and mortality globally.
• Serrated adenocarcinoma, a distinct CRC variant, accounts for approximately 7.5% of all CRCs.
• Serrated polyps are implicated as the origin of 10-15% of sporadic CRCs, possessing significant malignant potential.

Purpose of the Study:

• To define the histopathological and molecular characteristics of serrated adenocarcinoma.
• To differentiate serrated adenocarcinoma from conventional adenocarcinoma and other CRC subtypes.
• To elucidate the molecular pathways, including genetic mutations and methylation patterns, involved in serrated adenocarcinoma development.

Main Methods:

• Histopathological analysis using established criteria for serrated adenocarcinoma.
• DNA expression analysis of 7928 genes in serrated and conventional adenocarcinomas.
• Investigation of BRAF mutations, CpG island methylation (CIM), and microsatellite instability (MSI) including hMLH1 and MGMT methylation.

Main Results:

• Serrated adenocarcinomas were confirmed as a distinct molecular entity.
• Key molecular features include early oncogenic BRAF mutations, excess CIM, and varying MSI levels (16% high-level MSI, 29% low-level MSI).
• Distinct gene expression profiles were observed, with down-regulation of EPHB2, PTCH, and up-regulation of HIF1alpha in serrated adenocarcinomas.

Conclusions:

• Serrated adenocarcinoma represents a unique pathway in colorectal cancer development.
• Histopathological and molecular profiling are crucial for accurate diagnosis and classification.
• Understanding these distinct features may lead to improved diagnostic and therapeutic strategies for this CRC subtype.