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. The gene discussed is COL3A1; the disease is small cell lung carcinoma.