FGFR1 Amplification in Squamous Cell Carcinoma of the Lung with Correlation of Primary and Metastatic Tumor Status

Background: The FGFR1 gene can be amplified in squamous cell carcinoma of the lung (SqCC). The aim of this study was to compare FGFR1 status with stage and matched primaries with metastases. Methods: Cases with FGFR1 fluorescence in situ hybridization (FISH) testing performed from 2000 to 2013 were evaluated for amplification status and clinicopathologic features. Results: Of the 336 cases tested by FGFR1 FISH, 52 (15%) were positive for amplification. Eight (13%) of 60 N0 cases and eight (17%) of 46 N1 or N2 cases were amplified, with no statistically significant difference. Of the 24 cases with matched primary and metastatic tumors, 22 (92%) were synchronous and one (4%) had discordant amplification. Conclusions: Frequency of FGFR1 amplification is similar in SqCC with and without lymph node metastases, but status in metastatic sites may be discordant from the primary in a small subset of cases, which may affect the decision to perform testing of metastatic SqCCs.