Molecular and clinicopathological features of colorectal adenocarcinoma with enteroblastic differentiation

Colorectal adenocarcinoma with enteroblastic differentiation (CAED) is a rare subtype of colorectal malignancy with expression of enteroblastic markers (glypican 3, SALL4, AFP); however, the clinicopathological and epidemiological features are not fully elucidated.

The aims of this study were to elucidate and establish the molecular and clinicopathological characteristics of CAED.

In addition to three cases recently diagnosed as CAED, colorectal carcinoma (CRC) with expression of enteroblastic markers were selected by using immunohistochemistry (IHC) on tissue microarrays of 988 advanced CRC. We employed next-generation sequencing (NGS) and Sanger sequencing for the detection of genetic alterations. IHC for p53 and HER2, HER2-FISH and MSI status was also investigated. Survival analyses for clinicopathological parameters were performed using Kaplan-Meier methods.

Thirty-nine cases (4.0%) were positive for at least one enteroblastic marker. Histological evaluation of the total of 42 cases revealed that 10 contained tumour cells with clear cytoplasm. Enteroblastic marker-positive cases had aggressive behaviour and poor prognosis. NGS revealed TP53 as the most frequently mutated gene. The rate of HER2-positive cases and MSI-H cases was 9.5% (four of 42) and 12.2% (five of 41), respectively. Among these 42 cases, there were no molecular and clinicopathological differences according to the presence of tumour cells with clear cytoplasm.

Enteroblastic marker-positive CRC could be grouped together as CAED regardless of clear cell cytoplasm. Using this definition, the frequency of CAED is 4.0% and has a poorer prognosis than that for conventional CRCs. HER2 targeted therapy would be a meaningful treatment for CAED, and CAEDs contain both MSI-H and MSI-stable CRCs, although the MSS phenotype is dominant.