Histology does not accurately predict the clinical behaviour of bronchopulmonary carcinoids - results from an Icelandic population-based study]

Background and aims: Bronchopulmonary carcinoids (BPC) are rare tumors of neuroendocrine origin. These tumors are histologically classified into two distinctive forms, typical and the more malignant atypical BPC. We evaluated the epidemiology and results of treatment for BPC in Iceland with special emphasis on how atypical vs. typical histology relates to clinical behavior. Material & methods: This retrospective nation-wide study included all cases of BPC diagnosed in Iceland from 1955-2005. Histology of all the cases was reviewed and survival was based on data obtained from medical records and vital statistics. Results: BPC was diagnosed in 64 patients (22 males, mean age 49 yrs.), accounting for 1.9% of all lung neoplasms in Iceland. Average tumor-diameter was 2.5 cm (range 0.4-5.5), with typical histology in 54 (84%) and atypical in 10 patients (16%). Altogether 56 patients (87.5%) were operated on, most with lobectomy (82.1%). Forty eight patients were diagnosed in TNM stage 1, two patients in stage 11, four patients had mediastinal lymph node metastases (stage 111) and distant metastases were diagnosed in 6 patients (stage IV), 2 of whom had typical histology. At follow-up, 5 out of 64 patients had died of the disease (7.8%), two of them with typical histology. Five-year disease specific survival was 96% for patients with typical and 70% with atypical histology (p<0.05). Conclusion: BPCs usually behave as benign neoplasms, with excellent long-term survival after surgical removal. Metastases are more common in patients with atypical histology (40%), and their survival is worse. However patients with typical histology can metastasize (14.8%) and die from the disease. Therefore, histology (typical vs. atypical) can not be used with certainty to predict the clinical behaviour of these tumors.