Expression of HER2 in colorectal cancer does not correlate with prognosis.

Estimation of HER2 membranous expression is routinely used in breast and gastric cancers, as both a prognostic and a predictive factor. To date there is no evidence for similar application of HER2 expression in colorectal cancer (CRC) cells. In CRC, HER2 is sometimes overexpressed in the cell membrane and very often in the cytoplasm. This study was conducted to determine possible correlations between both membranous and cytoplasmatic expression of HER2 in CRC cells and the outcome of the disease. The prognostic significance of combined staining intensity in the cell membrane and cytoplasm in the entire CRC cell was also investigated. HER2 expression in resectable colorectal adenocarcinoma cells was evaluated by immunohistochemistry in specimens taken from 202 patients. The percentage of cancer cells with membranous or cytoplasmatic reactions and the staining intensity of the reaction in the whole cell were recorded. A membranous reaction was present in 27% of cases, and cytoplasmatic reaction in 66% of cases. The total staining intensity in the entire cell was evaluated as moderate (2+) in 32% of cases and strong (3+) staining in 15%. There was no correlation found between either membranous or cytoplasmatic HER2 expression and survival. Furthermore combined staining intensity did not provide any prognostic information. We conclude that HER2 expression in CRC does not correlate with prognosis.