Abstract

Bronchial carcinoid tumors are uncommon malignant neuroendocrine tumors that account for 2% of lung cancers. The main diagnostic tools are contrast-enhanced thoracic computed tomography (CT) and bronchoscopy. Early diagnosis is crucial because surgical excision is the primary treatment. The authors report a 32-year-old male patient with the smallest typical bronchial carcinoid tumor reported in the literature. The patient presented with chest pain for one month and recurrent pneumonia. Thoracic CT revealed an unclear 1 cm perihilar mass. Positron emission tomography CT showed a non-metabolic 1.4 cm nodule in the superior segment of the right lower lobe. The tumor was visualized via fiberoptic bronchoscopy, and initial biopsies were taken. Definitive diagnosis and curative treatment were achieved via segmentectomy. Bronchoscopy should be performed on middle-aged patients without comorbidities who experience recurrent pneumonia or have small hilar or perihilar masses on imaging.

Introduction

Bronchial carcinoid tumors (BCTs) are rare, solitary, slow-growing malignancies arising from neuroendocrine cells of the bronchial epithelium (1). Segmental and subsegmental BCTs constitute 80-90% of all cases (2). Well-differentiated BCTs are categorized into low-grade typical carcinoids (TCs), which have a favorable prognosis, and intermediate-grade atypical carcinoids (ACs), which carry a poorer prognosis (3). TCs are more common than ACs, with a ratio of 8-10:1 (4).

Most patients present with symptoms such as cough, dyspnea, or recurrent pneumonia; however, 25-39% remain asymptomatic due to the indolent nature of these tumors (5, 6).

Contrast-enhanced computed tomography (CT) is the primary imaging modality for detecting BCTs. Common CT findings include perihilar or hilar masses, endobronchial nodules, and signs of bronchial obstruction—such as atelectasis, post-obstructive pneumonitis, or air trapping (7, 8). Perihilar and hilar masses may also be associated with hilar or mediastinal lymphadenopathy secondary to metastasis or recurrent infection (7).

Definitive diagnosis relies on histopathological and immunohistochemical evaluation of tissue samples. Bronchoscopy remains an essential tool for confirming diagnosis, assessing bronchial wall invasion, and enabling therapeutic removal of endobronchial lesions, which may resolve associated atelectasis (9).

Here, we present what to our knowledge is the smallest TC reported in the literature—undetectable as a discrete perihilar mass on non-contrast CT yet clearly visualized by fiber-optic bronchoscopy (FOB).

Case Report

A 32-year-old man was referred to our pulmonology clinic for evaluation of recurrent pneumonia over the preceding year. He reported one month of chest pain. His medical history was unremarkable, and he smoked three cigarettes daily for 10 years. Family history included an unspecified malignancy in a grandparent. Physical examination and laboratory tests were normal.

Non-contrast CT performed at an outside facility revealed a 1-cm right perihilar lesion, initially suspected to represent a lymph node (Figure 1), prompting a positron emission tomography-CT (PET-CT). PET-CT demonstrated a small, slightly hyperdense 1.4-cm nodular lesion in the superior segment of the right lower lobe (RLL) without ¹⁸F-fluorodeoxyglucose (18F-FDG) uptake (Figure 2). Contrast-enhanced brain magnetic resonance imaging showed no metastatic disease.

FOB revealed near-complete obliteration of the superior segmental bronchus of the RLL by a smooth, hypervascular, cherry-red polypoid mass (Figure 3). Multiple punch biopsies were obtained, and histopathology indicated a carcinoid tumor, favoring TC. The patient subsequently underwent segmentectomy with bronchoplasty after multidisciplinary surgical review. Pathology confirmed a 1.4×1.1×0.9 cm TC. The sampled right hilar and infrahilar lymph nodes showed no involvement. No recurrence was detected during three years of postoperative follow-up, and he remains under annual surveillance.

Discussion

BCTs are more common in females and white patients, affecting individuals across all age groups. Mean age at diagnosis is approximately 55 years for ACs and 45 years for TCs (10). Although BCTs are not classically linked to carcinogen exposure, smoking is associated with their occurrence (11). Our patient’s demographic profile—middle-aged, white, and a smoker—aligns with known epidemiologic patterns.

Typical symptoms include chest pain, recurrent pneumonia, hemoptysis, and wheezing due to bronchial obstruction (7). Carcinoid syndrome is rare and typically associated with metastatic disease. The mediastinal lymph nodes are the most common metastatic site (12). Consistent with prior studies, the patient with localized TC presented with chest pain and recurrent pneumonia without features of carcinoid syndrome. The diagnosis is often delayed, even when symptoms are apparent. For example, patients with recurrent pneumonia may undergo years of evaluations before receiving a definitive diagnosis (13). Similarly, our patient sought care at multiple facilities for recurrent pneumonia and was treated with several courses of antibiotics over the span of a year before the TC was ultimately identified at our center.

TCs commonly appear as well-circumscribed ovoid or round opacities on CT, with 75-77% located centrally in the main, lobar, or segmental bronchi (14). TCs commonly arise in the right lung and middle lobe (13). The tumor in this case originated in the segmental bronchus of the RLL, consistent with these findings. Most BCTs measure 2-5 cm (7), whereas the tumor in our patient was significantly smaller and among the smallest reported. Although contrast-enhanced CT can detect small carcinoids, the initial non-contrast CT contributed to diagnostic difficulty.

PET-CT is a widely used imaging technique to assess thoracic cancers. PET-CT generally has limited value for well-differentiated BCTs, with sensitivity increasing with higher grade, from TCs to ACs (15). The absence of 18F-FDG uptake in this case aligns with expectations for TC.

Bronchoscopy remains crucial for evaluating BCTs, enabling direct visualization and biopsy. The tumor’s appearance—hypervascular, fragile, and polypoid—is characteristic of TC (9). Due to inadequate sampling and small size, more than 30% of BCTs require surgical resection for definitive diagnosis (16), as occurred in this patient.

Early detection is vital because surgical resection provides excellent outcomes in localized BCTs (17). Although TCs are less aggressive than ACs, they metastasize to regional lymph nodes in 4-20% of cases (18). Prognosis correlates more strongly with nodal status than with histologic subtype; 5-year survival reaches 100% in N0 patients for both TC and AC, while it decreases to 90% and 78.8% in N1 patients for TC and AC, respectively (19). Tumor size <3 cm also correlates with better outcomes (20). The patient with a small N0 TC underwent a segmentectomy and experienced an uneventful postoperative course with no recurrence at three years.

Conclusion

Clinicians should be aware of BCTs in middle-aged smokers without comorbidities presenting with recurrent pneumonia. Early diagnosis of BCTs is crucial, as surgical excision is curative for localized carcinoids. Contrast-enhanced thoracic CT is the mainstay of imaging for detecting carcinoids; however, small TCs may be radiologically occult. We recommend that physicians carefully examine the hilar and perihilar areas on CT scans and perform FOB to identify potential endobronchial tumors.