Prevalence estimation of microsatellite instability in colorectal cancers using tissue microarray based methods – A tertiary care center experience

Aim: Microsatellite instability (MSI) pathway is known to be implicated in carcinogenesis of 15% colorectal carcinomas (CRC), including 2%–3% of cases of Lynch syndrome, as per western literature. MSI status has important prognostic and therapeutic implications. The prevalence of MSI in Indian CRC patients is unknown. We aimed to determine the prevalence by studying 231 consecutive unselected cases of CRC. Methods: Tissue microarrays using duplicate cores per case for 141 cases, and whole tissue sections for 90 cases, were used. Immunohistochemistry with four mismatch repair (MMR) markers – MLH1, MSH2, MSH6, and PMS2 was performed. Molecular analysis for MSI status was performed in 18 randomly selected cases. Correlation with various clinical and histopathological features was done using univariate and multivariate analysis. Results: Loss of MMR immunohistochemical (IHC) was seen in 53/231 cases, i.e. 22.94% (95% confidence interval 17.52%–28.36%). MLH1-PMS2 dual loss comprised 13.9%, MSH2-MSH6 7.4%, and isolated PMS2 loss in 1.73% of cases. Univariate analysis showed significant association with age (<60 years), right-sided tumor location, histologic type, high grade, the presence of severe intratumoral lymphocytic (ITL) and peri-tumoral lymphocytic response, and N0 nodal stage. On multivariate analysis, independent variables were age < 60 years, right-sided location, and severe ITL. Molecular testing for MSI corroborated with the IHC results. Conclusion: The study results show a slightly higher prevalence of MSI-H phenotype, compared to Western literature, stressing the need for more widespread testing for better clinical management and identification of possible hereditary colon cancer syndrome.

An Unusual Case of Lepromatous Leprosy with Elastolysis and Atrophic Lesions

A 48-year-old lady presented with multiple, asymptomatic papules on upper trunk and upper extremities of 4 years duration. She gave a history of similar lesions/papules which used to heal earlier also, in a couple of weeks/months with atrophy. She had consulted many physicians and dermatologists without any relief. Biopsy from a papule showed dense nodular collection of foamy histiocytes in dermis in close proximity of neurovascular bundle. Special stain revealed absent elastic fibres in areas with infiltration. The case was diagnosed as lepromatous leprosy with elastolysis. Unusual features observed in the patient were predominant involvement of sun-exposed areas and atrophy. These signs and symptoms in the patient probably, mislead clinicians away from the diagnosis of leprosy.