Section examined shows an moderately differentiated adenocarcinoma composed of irregular infiltrating glands, focal cribriform architecture, and malignant epithelial cells exhibiting moderate nuclear pleomorphism, hyperchromatic enlarged nuclei, conspicuous nucleoli, and moderate eosinophilic cytoplasm. Frequent mitotic figures are identified, and tumor groups are set within a desmoplastic stroma.
Immunohistochemistry for Mismatch Repair Proteins:
Immunostaining for MLH1, PMS2, MSH2, and MSH6 demonstrates preserved nuclear expression in tumor cells for all four mismatch repair proteins. Internal control cells show appropriate reactivity.
Fourteen referred paraffin block for immunostaining of Rt. colon adenocarcinoma grade 2.
One section was done from submitted blocks.
Rt. colon mass, excision:
Comment:
The retained expression of MLH1, PMS2, MSH2, and MSH6 supports proficient DNA mismatch repair status and argues against microsatellite instability-high phenotype. Correlation with clinical and molecular findings is recommended where clinically indicated.