Included variables: CD13 expression in stromal cells (negative expression (ref.)vs. positive expression), CD13 expression in NSCLC tumor cells (negative expression (ref.)vs. positive expression), tumor stage (stage I (ref.)vs. stage II vs. stage III), lymph node status (pN0 (ref.)vs. pN1 vs. pN2 vs. pN2), and tumor histology (squamous cell carcinoma vs. adenocarcinoma vs. large cell carcinoma). The gene discussed is ANPEP; the disease is non-small cell lung carcinoma.