MLH1 and neoplasm: As expected, immunohistochemical staining demonstrated that the tumor was MLH1 negative and MSH2 positive (Fig. 3), which was in agreement with the germline mutation in MLH1. A microsatellite instability (MSI) analysis diagnosed the tumor as MSI high using the National Cancer Institute panel (NCI panel: D2S123, D5S346, D17S250, BAT25 and BAT26); replication errors were observed in four microsatellite markers [MSI-H (4/5)] (Fig. 4).