Pulmonary and thymic carcinoid tumors.

Carcinoid tumors of the lung and bronchi are usually benign lesions with no influence on life expectancy, although occasionally, they are malignant with a poor prognosis. Between these two extremes are atypical carcinoids, which can be slow-growing tumors with an average 5-year survival of 60% and an average 10-year survival of 40%. The myriad names used to describe these lesions complicates the understanding of their behavior, especially as the term carcinoid is used to describe the complete spectrum of disease or exclusively the benign well differentiated lesions with an excellent prognosis. Thymic carcinoids are uncommon lesions. Their prognosis is poor, even in cases that appear favorable in terms of resectability and histology. Pulmonary carcinoids present uncommonly with a paraneoplasic syndrome. Both carcinoid and Cushing syndromes are seen with approximately 2% of these lesions. Cushing syndrome can be present in as many as one-third of patients with thymic carcinoids but an association with the carcinoid syndrome has never been described.