COL4A1 and lung cancer: COL4A1 expression in lung cancer has been previously detected in stromal fibroblasts surrounding tumor cells by mRNA in situ hybridization [34] and discontinuous collagen α1(IV) protein expression has been detected around well-differentiated clusters in ADCs [35], results which are similar to the present findings i.e. strong collagen α1(IV) immunoreactivity in the stroma of ADC.