AbstractBackground and ObjectivesA disintegrin and metalloprotease 12 (ADAM12) has multiple domains and functions, and it plays important roles in the development of cancer. We conducted a retrospective study to determine whether the expression of the membrane type of ADAM12 (ADAM12‐L) could be a prognostic factor in resected pathological (p‐) stage I lung adenocarcinoma.MethodsADAM12‐L mRNA expression was quantified by a reverse‐transcription polymerase chain reaction in tissue samples from 84 completely resected p‐stage I lung adenocarcinoma patients. The patients were divided into ADAM12‐L‐Low and ADAM12‐L‐High groups, and correlations with clinicopathologic features were obtained.ResultsFive‐year survival rates of the ADAM12‐L‐Low and ADAM12‐L‐High groups were 95.1% and 71.9%, respectively. The postoperative prognosis for the ADAM12‐L‐High group was significantly poorer than for the ADAM12‐L‐Low group (P = 0.006). Multivariate analysis confirmed that high expression of ADAM12‐L was an independent factor for poor prognosis (P = 0.007, hazard ratio 8.288). The ADAM12‐L‐High group was less differentiated and had a significantly higher rate of cancer recurrence.ConclusionsADAM12‐L mRNA expression is an independent prognostic factor in resected p‐stage I lung adenocarcinoma, and is significantly correlated with tumor differentiation stage and postoperative cancer recurrence. J. Surg. Oncol. 2009;100:267–272. © 2009 Wiley‐Liss, Inc.