OBJECTIVETo study the possible clonal origin of neuroendocrine cells in colorectal adenocarcinoma.

METHODSTwenty-six microsatellite loci were screened using laser capture microdissection, DNA extraction and whole genome amplification. Microsatellite instability (MSI) and loss of heterozygosity (LOH) in adenocarcinoma cells and neuroendocrine cells amongst 30 cases of colorectal carcinoma with neuroendocrine differentiation were detected using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP)-silver staining. The mutation status of p53 was evaluated by PCR-sequencing. The clonal origin of neuroendocrine cells in colorectal adenocarcinoma was determined.

RESULTSAmongst the 30 cases studied, the prevalence of MSI was 16.9% while that of LOH was 8.5%. The rate showed no statistically significant difference between adenocarcinoma cells and neuroendocrine cells. In 6 cases, the microsatellite alteration was entirely consistent. In 23 cases, the rate of microsatellite alteration consistency was greater than that of inconsistency. In 1 case, the consistency and inconsistency rates were identical. There was statistically significant difference between consistency and inconsistency of microsatellite alteration. The prevalence of p53 mutation was 16.7% which was the same for both adenocarcinoma cells and neuroendocrine cells.

CONCLUSIONSAdenocarcinoma cells and neuroendocrine cells in colorectal adenocarcinoma with neuroendocrine differentiation have similar biologic changes. It is likely that they are of identical origin.