[SERRATED COLORECTAL ADENOCARCINOMA]

Area of Science:

• Gastroenterology
• Oncology
• Molecular Pathology

Background:

• Serrated lesions are recognized as precursors to colorectal cancer, accounting for 10-15% of sporadic cases via the serrated pathway.
• Serrated adenocarcinoma exhibits unique morphological criteria distinguishing it from traditional colorectal adenocarcinomas.
• WHO classification acknowledges the malignant potential of serrated lesions.

Observation:

• A 67-year-old woman presented with constipation, abdominal pain, and distention.
• Colonoscopy revealed a 3.0 x 3.0 cm tumor at the hepatic flexure and a sigmoid polyp.
• Biopsies confirmed serrated adenocarcinoma and tubulovillous adenoma with severe dysplasia.

Findings:

• Genetic analysis of the tumor showed high microsatellite instability and a positive CpG island methylator phenotype (CIMP+).
• The patient underwent right hemicolectomy and sigmoid polyp removal; final pathology confirmed clear margins and no lymph node metastasis.
• Serrated adenocarcinoma is characterized by microsatellite instability and CIMP+.

Implications:

• Microsatellite instability in serrated adenocarcinoma may indicate a more favorable prognosis due to enhanced tumor immunogenicity.
• This subtype of colorectal cancer demonstrates a higher response rate to fluoropyrimidine-based therapies.
• Accurate diagnosis and understanding of serrated adenocarcinoma's molecular profile are crucial for tailored clinical management.