Abstract: Objective To investigate the expression of anaplastic lymphoma kinase (ALK) gene fusion antibody in non-small cell
lung cancer (NSCLC) and explore the clinicopathological significance. Methods Using manual immunohistochemistry (IHC)
with D5F3 rabbit monoclonal antibody, we detected the expression of ALK gene fusion protein in 519 cases of NSCLC. The
relations of ALK fusion protein with the clinical characteristics of the patients and the histological classification of the tumors
were analyzed. The expressions of ALK fusion protein were compared between surgical specimens and biopsy samples, and
the consistency of manual IHC results was evaluated with the results of a fully automated IHC instrument and fluorescence in
situ hybridization (FISH). Results The positivity rate of ALK fusion protein was 11.37% (59/519) among the cases detected by
manual IHC. The patients tended to have a young age of onset (P=0.048) and most of the tumors were adenocarcinoma. In the
surgical specimens, ALK fusion protein was expressed mostly in invasive mucinous adenocarcinoma (P<0.01), and it was a
high risk factor of lymph node metastasis [OR=2.188(95%C.I:1.161-4.122)]. No statistical difference was found in the test results
of manual IHC between surgical specimens and biopsy samples. The results by manual IHC suggesting a strong expression
were consistent with the results by automated IHC and FISH. Conclusion Manual IHC can be reliable for screening ALK
fusion arrangement in patients with NSCLC.