ITGA5 and small cell lung carcinoma: In the present study, we evaluated gene expression profiles using a set of twenty-four patients with surgically resected PNENs, including SCLC, and identified six fibrogenic genes: COL1A2, COL3A1, COL5A2, ITGA5, ITGAV, and ITGB1 up-regulated in PNECs and down-regulated in PNETs.