Immunosurveillance in Colorectal Carcinomas with Microsatellite Instability

Tumour infiltrating lymphocytes have been associated to a better prognosis in colorectal cancers. Microsatellite unstable tumours present a greater infiltration by these immune cells when comparing to microsatellite stable tumours. It has been suggested that lymphocytic infiltration may be an indicator of a host immune response against tumour cells and therefore, contribute to a better prognosis. High microsatellite instability (MSI-H) tumours have been shown to bare a better prognosis and some authors believe that TILs infiltration take a part in this. Nonetheless, the significance of tumour infiltrating lymphocytes (TILs), their distribution and prognostic value are still unclear. The aim of this review is to summarize the current evidence on tumour infiltrating lymphocytes characteristics, distribution, activity and relation to prognosis in microsatellite unstable colorectal tumours.