Transformation from adenocarcinoma to squamous cell carcinoma associated with long-term administration of EGFR-TKIs.

Although patients with non-small cell lung cancer exhibiting mutations generally respond to tyrosine kinase inhibitors (TKIs), the majority of patients acquire resistance ~1 year after treatment. T790M mutations, or amplifications and phenotypic transformations contribute to the mechanism of EGFR-TKI resistance. The transformation of small cell lung cancer frequently occurs, although few convert to squamous cell carcinoma associated with the administration of EGFR-TKIs. The current study reports a case of -mutated adenocarcinoma of the lung that transitioned to squamous cell carcinoma in association with long-term EGFR-TKIs administration.