Correct!
4. Pulmonary carcinoid tumors frequently result in the carcinoid syndrome
Both typical and atypical carcinoid tumors are true malignancies, although typical carcinoid tumors are often relatively indolent neoplasms that are associated with a generally good prognosis following complete surgical resection. Most pulmonary carcinoid tumors (60-70%) present as centrally located masses, arising from the main, lobar, or segmental bronchi. Due to their central endobronchial location, pulmonary carcinoid tumors often present as hilar or perihilar masses on chest radiography, often associated with post-obstructive changes, such as atelectasis, consolidation, or air trapping. At thoracic CT, the endobronchial nature of carcinoid tumor is often readily apparent, and the lesions often show calcification. Intense enhancement following intravenous contrast administration at thoracic CT is common with carcinoid tumors, owing to their relatively vascular nature. However, pulmonary carcinoid tumors often do not show significant tracer accumulation at 18FDG-PET scanning- this is one of the well-known pitfalls in tumor detection and staging using 18FDG-PET. Pulmonary carcinoid tumors are uncommonly associated with the carcinoid syndrome- abdominal cramps, flushing of the face, neck or upper chest, diarrhea, palpitations, hypotension, and wheezing. The carcinoid syndrome is mediated by release of vasoactive substances, such serotonin release, and occurs most commonly in patients with gastrointestinal carcinoid tumors, frequently win the setting of liver metastases.
Neuroendocrine cell neoplasms arise from Kulchitzky cells in the bronchial mucosa and include “typical” carcinoid tumors, “atypical” carcinoid tumors, large cell neuroendocrine neoplasms, and small cell carcinoma, in increasing order of aggressiveness. Pulmonary carcinoid tumors account for more than 25% of all carcinoid tumors and 1-2% of pulmonary neoplasms. Most (80-90%) carcinoid tumors are “typical” carcinoid tumors, with the remaining 10-20% “atypical” carcinoid tumors. Men are about as equally affected as women, with some reports suggesting a female predominance, and others indicating a male predominance; men are more commonly affected with atypical carcinoid tumors. The age of presentation is wide, averaging about 46 years old, although carcinoid tumors are among the commonest pulmonary neoplasms in children and adolescents. Typical carcinoid tumors are unassociated with smoking, whereas some association with smoking with atypical carcinoid tumors has been recognized.
Carcinoid tumors tend to present with symptoms of central airway obstruction, such as cough, wheezing, and hemoptysis. Carcinoid tumors are occasionally detected asymptomatically. Atypical carcinoid tumors may be more peripherally located than typical carcinoid tumors, and therefore present at a slightly later age than typical carcinoid tumors.
Pulmonary carcinoid tumors commonly present as hilar or perihilar masses at chest radiography, associated with post-obstructive atelectasis, pneumonitis, consolidation, or air trapping. Thoracic CT commonly shows a round or oval endobronchial lesion, associated with post-obstructive atelectasis or air trapping, arising in the main, lobar, or segmental bronchi. Mucus plugging distal to the lesion is common. Carcinoid tumors may be located distal to segmental airways, and then are classified as peripheral, in 16-40% of patients. The relationship of the tumor to the airway is often not evident for peripheral lesions, and these tumors often present as solitary pulmonary nodules. Calcification may be seen in up to 30% of lesions at CT but is often not appreciable at chest radiography, and is more commonly encountered in central lesions. Typical and atypical carcinoid tumors closely resemble one another at imaging, although atypical carcinoid tumors tend to be larger at diagnosis and more commonly associated with lymphadenopathy, reflecting their more aggressive nature. Atypical carcinoid tumors are more likely to be found in the lung peripheral than typical carcinoid tumors.
Contrast-enhanced thoracic CT in patients with carcinoid tumors often shows intense contrast enhancement of the lesion. However, lack of significant tracer utilization at 18FDG-PET is well-recognized with carcinoid tumors, but is not a universal finding, and occasionally typical carcinoid tumors are associated with increased tracer utilization at 18FDG-PET.
Pulmonary carcinoid tumors are generally treated surgically when possible, and outcomes are usually excellent. Post-operative survival is diminished with atypical carcinoid tumors compared with typical lesions, although still improved compared with bronchogenic carcinomas. The histopathological lesion classification and status of nodal involvement are the two most important factors influencing patient prognosis.
References