Clinical characteristics of the mixed form of neuroendocrine tumor in the lung: A retrospective study in 2501 lung cancer cases

BACKGROUND: A neuroendocrine tumor (NET) is a special kind of epithelial tumor with predominant neuroendocrine differentiation, which arises throughout the body, including the lung. A subpopulation of lung cancer patients suffer from the mixed (combined) form of NET with components of non-neuroendocrine carcinoma. However, the clinical characteristics of the mixed form of NET are not well established. METHODS: We analyzed 2501 consecutive cases of primary lung cancer from 2009 to 2011. The diagnosis, histology, therapy, and outcome were collected. RESULTS: A total of 22 patients were enrolled. The occurrence rate of lung cancer was 0.9%. Neither gender (1.2% and 0.3% for male and female, respectively, P = 0.35) nor age (0.6% and 1.3% for patients aged ≤60 and >60, respectively, P = 0.13) was associated with the onset of this disease; however it has become more frequent in recent years (0.6% and 1.6% at the time ≤ and >2010 respectively, P = 0.03). This cohort of 22 patients had a median survival of 60.0 months (95% confidence interval: 14.3–105.6 months). Patients with metastatic disease (60 months and not reached [NR], P = 0.18) or a small-cell lung cancer component tended to have a shorter survival (35 months and NR, P = 0.16). Patients who underwent surgery had a significantly longer survival period (NR and 17.0 months, P = 0.001). CONCLUSIONS: A mixed form of NET in the lung is a rare disease. While stage and histology might influence prognosis, surgery is the critical factor for long-term survival.