Microsatellite instability in young patients with mucinous colorectal cancers – characterization using molecular testing, immunohistochemistry, and histological features

CONTEXT: The incidence of colorectal cancers (CRCs) in young Indian patients is higher than the international average. CRCs in young patients are commonly of mucinous type and show microsatellite instability (MSI). AIMS: To ascertain the MSI status of mucinous CRCs in patients ≤40 years of age by molecular testing and to correlate this with immunohistochemical (IHC) analysis and tumor histology. SUBJECTS AND METHODS: Archived formalin-fixed paraffin embedded tissue blocks of 30 young mucinous CRC patients were retrieved. MSI testing was done using two mononucleotide markers – BAT26 and NR24. IHC analysis was done using MLH1, MSH2, and MSH6. Histological features of all cases were studied. Data were analyzed using the SPSS software and the Pearson's chi-square test and Fisher's exact test. RESULTS: Eight out of 30 cases (26.7%) showed MSI by molecular testing. IHC identified seven of these cases. Histological features showing a statistically significant association with MSI were the presence of a well-differentiated adenocarcinoma component (P = 0.003), peritumoral lymphocytes (P = 0.002) and tumor budding (P = 0.021). CONCLUSION: The detection of defective mismatch repair (MMR) proteins using IHC for MLH1, MSH2, and MSH6 and molecular testing using BAT26 and NR24 appears to be a good protocol to detect CRCs with MSI. Histology could be useful in identifying cases that require screening for presence of MMR protein defects

Infraorbital nerve schwannoma: A rare cause of upper jaw swelling.

Introduction: Schwannoma of the infraorbital nerve is a rare entity, with lesser than a dozen cases reported in literature and only one from India. Report: This article reports a 23-year-old male presenting with a painless swelling in the cheek, which was eventually diagnosed as infraorbital nerve schwannoma. He underwent a complete excision of the tumor via a Caldwell Luc approach and continues to be disease free on 3 year follow-up. Conclusion: Despite its rarity, infraorbital nerve schwannomas should be considered in the differential diagnosis, of upper jaw swelling. We recommend the Caldwell Luc approach as safe, effective and cosmetically acceptable, for anteriorly based infraorbital schwannomas, and review literature on this unusual entity