Carcinoid tumors (TC and AC) (account for 1% to 2% of lung malignancies), show similar characteristic histologic patterns and the differential diagnoses is based on mitotic index and proliferative status (2 mitosis per 10 high-power field and 5% Ki-67 positive staining for TC, and 2–10 mitosis per 10 high-power field and 5%–20% Ki-67 positive staining or the presence of necrosis for AC). This evidence concerns the gene MKI67 and carcinoid tumor.