Bronchial Carcinoid Tumors of the Thorax: Spectrum of Radiologic Findings

Abstract

Bronchial carcinoid tumors are neuroendocrine neoplasms that range from low-grade typical carcinoids to more aggressive atypical carcinoids and therefore demonstrate a wide spectrum of clinical behaviors and histologic features. Typical and atypical bronchial carcinoids have similar imaging features. Because most bronchial carcinoids are located in central airways, radiologic findings are usually related to bronchial obstruction. Central bronchial carcinoids manifest as an endobronchial nodule or hilar or perihilar mass with a close anatomic relationship to the bronchus. The mass is usually a well-defined, round or ovoid lesion and may be slightly lobulated at radiography and computed tomography (CT). Associated atelectasis, air trapping, obstructing pneumonitis, and mucoid impaction may also be seen. Peripheral bronchial carcinoids appear as solitary nodules. Calcification is common and is easily visualized at CT. Bronchial carcinoids demonstrate high signal intensity on T2-weighted and short-inversion-time inversion recovery magnetic resonance images. Prognosis of bronchial carcinoids is highly dependent on histologic findings: Atypical carcinoids have certain features that suggest a more aggressive nature. Typical bronchial carcinoids generally have an excellent prognosis, whereas atypical bronchial carcinoids have a worse prognosis. Therefore, understanding the histologic, clinical, and radiologic features of bronchial carcinoids facilitates accurate diagnosis and helps optimize surgical planning.

Pulmonary neuroendocrine/carcinoid tumors

“…Well-defined, centrally located tumors involving the airway with calcification, punctate or diffuse, are considered characteristic on CT scan. 21 However, additional investigation and staging with fluorodeoxyglucose (FDG) -PET scanning remains controversial. Due to the lower metabolic activity of carcinoid tumors, FDG uptake in PET scanning often demonstrates low uptake (equivocal in comparison to mediastinal uptake) compared with high-grade nonsmall cell cancers.…”

“…It has also been reported that tumors are more common in the right lung, presumably related to the larger at-risk area of lung. 13,18,21 …”

Unusual lung tumours: an illustrated review of CT features suggestive of this diagnosis

“…It accounts for 0.5-2.5% of all primary lung tumours, and is subdivided into typical (80%) and atypical (20%) types [1] . It has a mean age of presentation of 45 years, younger than that for conventional bronchogenic carcinoma [33] . Typical carcinoid usually appears as a solitary, well-defined 1-3 cm oval or lobulated soft tissue nodule [1] .…”

“…In 15% of cases it arises within the lung periphery, in which case it may not be directly related to an airway on gross inspection [1] . Rarely, tumours are irregular or ill-defined [1,33] . Most endobronchial carcinoids have a large extraluminal component, and for this reason are termed 'iceberg' lesions [34] .…”

“…Consolidation, atelectasis or mucoid impaction distal to an endobronchial carcinoid are common presentations (Fig. 4) [33] . Approximately 30% of lesions demonstrate variable calcification or even ossification on CT [35] , although this is usually not detectable radiographically [33] .…”