Effect of cold ischemia time and storage temperature on anaplastic lymphoma kinase (ALK) expression in surgically resected lung cancer specimens.

Driver gene mutations in lung cancer serve as essential targets for personalized therapy. Ensuring the quality of resected specimens is crucial for accurate diagnosis. This study aimed to evaluate the correlation between cold ischemia time and anaplastic lymphoma kinase (ALK) expression in non-small cell lung cancer (NSCLC) specimens. ALK-positive lung cancers resected from a 47-year-old woman and a 69-year-old woman were analyzed. The resected tumor was divided into nine sections and fixed after different cold ischemia times (0-24 h). One specimen was stored at room temperature and the other under refrigerated conditions prior to fixation. ALK expression was assessed using an ALK immunohistochemical assay and quantified with bioimage analysis software by averaging the percentage of ALK-positive cells in ten randomly selected microscopic fields. To validate the effect of storage temperature in clinical practice, specimens from 642 patients who underwent radical pulmonary resection for lung adenocarcinoma between 2021 and 2025 were retrospectively analyzed. Cases stored at room temperature until fixation (n=458) were compared with those stored under refrigeration below 4 ℃ (n=184). Pathological evaluation showed ALK positivity up to 3 h after resection but negativity after 4 h in room temperature-stored specimens. In contrast, specimens stored under refrigerated conditions maintained ALK positivity even after 8 h of cold ischemia. Quantitative analysis confirmed a marked reduction in ALK-positive cells with increasing ischemia time (77.4% at 0 h vs. at 2.1% at 24 h) in room temperature-stored specimens. In the validation cohort, the refrigerated group demonstrated a significantly higher ALK positivity rate (3.8% vs. 0.2%; P<0.001). Prolonged cold ischemia time profoundly affects ALK status. Surgically resected tumors should be stored below 4 ℃ immediately after resection and fixed in formalin within 3 h at the latest.