Background Malignant transformation of oral lichen planus (OLP) to oral squamous cell carcinoma (OSCC) is controversial. C-MYC is a proto-oncogene involved in various solid tumours, including OSCC. Objectives To determine MYC status using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) in OLP lesions from 10 patients with progression to OSCC (group I) and to compare this with OLP lesions from patients without progression to OSCC (group II). Methods We constructed two tissue microarrays with 11 OSCC samples (group IA), 17 OLP samples from the same patients (group IB) and 13 OLP specimens from 12 control patients (group II). FISH evaluation of the MYC gains was determined in 100 nonoverlapping nuclei per sample. IHC evaluation was determined by calculating the percentage C-MYC expression in the epithelial cells. Results OSCC samples showed MYC copy number gains and C-MYC overexpression in 91% and 73% of cases, respectively. MYC gains were detected in 47% of samples from group IB and were absent from all samples from group II. C-MYC was overexpressed in 87% of cases from group IB and in only 44% of control specimens (group II). The differences in MYC status between groups IB and II were statistically significant. Conclusions OLP lesions in patients with progression to OSCC show MYC gains and C-MYC overexpression. In patients with severe OLP, determining MYC status may predict a subgroup of subjects with a higher risk of progression to OSCC. What's already known about this topic? Malignant transformation of oral lichen planus (OLP) to oral squamous cell carcinoma (OSCC) is controversial. Clinical and histological features of OLP lesions have limited prognostic value. What does this study add? OLP lesions from patients with progression to OSCC show MYC gains and C-MYC overexpression, not present in OLP lesions from patients without evolution to OSCC. Determining MYC status on some OLP lesions may predict a subgroup of patients with a higher risk of progression to OSCC. © 2013 The Authors BJD © 2013 British Association of Dermatologists.