Considering tissue heterogeneity in terms of the localized expression of particular molecules along with the above-mentioned immunohistochemical observation, we speculate that the extent of the upregulation of Cox-2 and its possible downregulation of E-cadherin may depend on microscopically specific sites such as the invasive front or the inside of cancer nests, which would not necessarily be reflected in any statistical analysis or in homogenized samples at all. The gene discussed is PTGS2; the disease is cancer.