Morphologic and molecular study of lung cancers associated with idiopathic pulmonary fibrosis and other pulmonary fibroses.

BACKGROUND: Primitive lung cancers developed on lung fibroses are both diagnostic and therapeutic challenges. Their incidence may increase with new more efficient lung fibrosis treatments. Our aim was to describe a cohort of lung cancers associated with idiopathic pulmonary fibrosis (IPF) and other lung fibrotic disorders (non-IPF), and to characterize their molecular alterations using immunohistochemistry and next-generation sequencing (NGS). METHODS: Thirty-one cancer samples were collected from 2001 to 2016 in two French reference centers for pulmonary fibrosis - 18 for IPF group and 13 for non-IPF group. NGS was performed using an ampliseq panel to analyze hotspots and targeted regions in 22 cancer-associated genes. ALK, ROS1 and PD-L1 expressions were assessed by immunohistochemistry. RESULTS: Squamous cell carcinoma was the most frequent histologic subtype in the IPF group (44%), adenocarcinoma was the most frequent subtype in the non-IPF group (62%). Forty-one mutations in 13 genes and one EGFR amplification were identified in 25 samples. Two samples had no mutation in the selected panel. Mutations were identified in TP53 (n = 20), MET (n = 4), BRAF (n = 3), FGFR3, PIK3CA, PTEN, STK11 (n = 2), SMAD4, CTNNB1, DDR2, ERBB4, FBXW7 and KRAS (n = 1) genes. No ALK and ROS1 expressions were identified. PD-L1 was expressed in 10 cases (62%) with only one (6%) case >50%. CONCLUSIONS: This extensive characterization of lung fibrosis-associated cancers evidenced molecular alterations which could represent either potential therapeutic targets either clues to the pathophysiology of these particular tumors. These findings support the relevance of large molecular characterization of every lung fibrosis-associated cancer.