Gastric Carcinomas With Lymphoid Stroma: Categorization and Comparison With Solid-Type Colonic Carcinomas

Area of Science:

• Gastroenterology
• Oncology
• Pathology

Background:

• Gastric carcinomas with lymphoid stroma represent a heterogeneous group.
• Distinguishing between Epstein-Barr virus (EBV)-associated, microsatellite instability (MSI)-associated, and other subtypes is crucial for understanding their distinct biological behaviors and clinical implications.
• Histologic features are often used for initial classification, but their reliability in identifying specific molecular subtypes in gastric cancer requires further investigation.

Purpose of the Study:

• To investigate whether specific histologic features can reliably differentiate gastric carcinomas with lymphoid stroma based on their association with EBV infection or MSI.
• To compare the clinicopathologic features of EBV-associated, MSI-associated, and non-EBV/non-MSI gastric carcinomas.
• To evaluate the utility of morphology versus ancillary testing in classifying these tumors.

Main Methods:

• A cohort of 17 solid-type gastric carcinomas with lymphoid stroma was identified and assessed for EBV and MSI status.
• Histologic features, including intratumoral germinal centers, eosinophils, necrosis, lymphocytes, and neutrophils, were analyzed.
• The study also included a comparison with 51 solid-type colorectal adenocarcinomas, including MSI-driven and non-MSI subtypes.

Main Results:

• In gastric cancer, EBV-associated carcinomas exhibited intratumoral germinal centers and eosinophils, and lacked necrosis, distinguishing them from MSI-associated and non-EBV/non-MSI types.
• In colorectal cancer, MSI-driven carcinomas showed increased intratumoral lymphocytes and neutrophils and less frequent distant metastasis compared to poorly differentiated carcinomas lacking MSI.
• Morphologic differences were observed, but ancillary testing confirmed EBV and MSI status.

Conclusions:

• Histologic examination may offer clues for classifying gastric carcinomas with lymphoid stroma, but ancillary molecular testing remains the more definitive method.
• Epstein-Barr virus (EBV)-associated gastric carcinomas and microsatellite instability (MSI)-associated gastric carcinomas (medullary carcinomas) possess distinct morphologic characteristics.
• The terms lymphoepithelioma-like carcinoma and medullary carcinoma should not be used interchangeably due to their differing underlying biology and potential clinical relevance.