Lung adenocarcinoma patients harboring anaplastic lymphoma kinase (ALK) gene rearrangements respond well to approved ALK inhibitors. However, to date, limited evidence is available regarding whether using circulating free tumor mRNA to identify aberrant ALK expression is possible, and its feasibility remains to be clearly addressed. The present study evaluated ALK expression by a one-step reverse transcription‑polymerase chain reaction (PCR) assay on the circulating free tumor mRNA from 12 lung adenocarcinoma patients. Additionally, the present study tested for ALK rearrangements by fluorescence in situ hybridization (FISH) and immunohistochemistry. A molecular genetic characterization was performed on tumor tissues and plasma samples. Aberrant ALK expression was detected in 2/12 patients using mRNA purified from plasma specimens and the results agreed with the FISH and immunohistochemistry findings of solid biopsy samples. The detection of aberrant ALK expression on circulating free tumor RNA may be feasible using a one‑step real‑time PCR assay and may be particularly helpful when a solid biopsy sample is not available.