Immunohistochemical analysis of a rectal adenocarcinoma tissue microarray (n = 234 tumours) demonstrated that APRIL protein was expressed in tumour cells and/or tumour stroma. Positive stromal expression was strong. In tumour cells expressing APRIL, intensity was weak, moderate or strong. The number of rectal adenocarcinomas with positive staining for APRIL protein. Percentage of the total (n = 234) is in parentheses. There was a significant correlation between tumour cell and stromal expression (p = 0.048). There was no significant association between tumour cell or stromal staining and age, gender, histological grade, tumour site or Duke's stage (all p > 0.20. Data not shown).