Marked 18-Fuorine-Fluorodeoxyglucose (FDG) Avidity of an Intrapulmonary Typical Carcinoid Tumor Manifesting as a Bronchocele in an Asymptomatic Middle-Aged Woman

BACKGROUND Intrapulmonary carcinoid tumors (ICTs) are malignant, slow-growing tumors classified as either: i) typical, less aggressive, well-differentiated tumors or ii) atypical, more aggressive, poorly-differentiated tumors. Most typical carcinoid tumors originate in the central airway and present with symptoms related to bronchial obstruction. In contrast, atypical carcinoids tend to occur more peripherally and are generally detected incidentally as a solitary pulmonary nodule (SPN). Typical carcinoid tumors usually do not exhibit increased metabolic activity on positron emission tomography with 18-fuorine-fluorodeoxyglucose (FDG PET) as would be expected for malignant tumors. In this case report, we present an unusual case of a typical, well-differentiated, peripheral carcinoid tumor showing marked FDG avidity manifesting as a bronchocele. We discuss the differential diagnoses and describe the diagnostic approach undertaken in this exemplary case of a common clinical problem. CASE REPORT A left upper-lobe, peripheral, 2-cm pulmonary nodule was incidentally identified on chest radiography of an asymptomatic 67-year-old female patient. Chest CT scan with intravenous (IV) contrast showed a noncalcified nodule with a branching pattern. Further evaluation with FDG PET/CT scan demonstrated marked FDG avidity. Post-surgical biopsy revealed a typical, well-differentiated, intrapulmonary carcinoid tumor. CONCLUSIONS Carcinoid tumors of the lung remain a diagnostic challenge for primary care physicians and radiologists due to their diverse clinical and radiological presentations. Peripheral carcinoid tumors usually present as an asymptomatic peripheral, solitary, pulmonary nodule, but isolated peripheral bronchocele has been described, as in our case. In addition, caution must be taken when utilizing FDG PET/CT scan for the evaluation of a possible lung carcinoid tumor, as an accurate value range of FDG uptake for diagnosis of these tumors has not been defined.