Objective: Cytokeratin20+/Cytokeratin7− (CK) is used as the characteristic immunophenotype of colorectal carcinomas (CRC) . Some new studies suggested that aberrant pattern CK20/CK7 can be identified in colorectal cancer with microsatellite instability (MSI). Our aim was to establish which factors may determine changing in this immunophenotype. Method: In 70 CRC, randomly selected, we performed immunohistochemical stains with CK20 and CK7 and analyzed the microsatellite status and BRAF mutations with real time PCR. Results: From the 70 CRC, 15 were MSI and 55 MSS (microsatellite stable) cases. 90 % of MSS cases diffusely expressed CK20 without CK7 expression. From the 15 MSI cases, 6 presented BRAF mutations. In MSI cases with BRAF mutations, CK20 was focally expressed or negative and CK7 was diffusely expressed. Conclusion: Cytokeratin7 positivity may be used to select BRAF mutated MSI colorectal carcinomas. Both CK7 and CK20 should be used for differential diagnosis of colorectal cancer.