Typical and Atypical Bronchopulmonary Carcinoid Tumors on FDG PET/CT Imaging

Malignant and Benign Tracheobronchial Neoplasms: Comprehensive Review with Radiologic, Bronchoscopic, and Pathologic Correlation

Tracheobronchial neoplasms are much less common than lung parenchymal neoplasms but can be associated with significant morbidity and mortality. They include a broad differential of both malignant and benign entities, extending far beyond more commonly known pathologic conditions such as squamous cell carcinoma and carcinoid tumor. Airway lesions may be incidental findings at imaging or manifest with symptoms related to airway narrowing or mucosal irritation, invasion of adjacent structures, or distant metastatic disease. While there is considerable overlap in clinical manifestation, imaging features, and bronchoscopic appearances, an awareness of potential distinguishing factors may help narrow the differential diagnosis. The authors review the epidemiology, imaging characteristics, typical anatomic distributions, bronchoscopic appearances, and histopathologic findings of a wide range of neoplastic entities involving the tracheobronchial tree. Malignant neoplasms discussed include squamous cell carcinoma, malignant salivary gland tumors (adenoid cystic carcinoma and mucoepidermoid carcinoma), carcinoid tumor, sarcomas, primary tracheobronchial lymphoma, and inflammatory myofibroblastic tumor. Benign neoplasms discussed include hamartoma, chondroma, lipoma, papilloma, amyloidoma, leiomyoma, neurogenic lesions, and benign salivary gland tumors (pleomorphic adenoma and mucous gland adenoma). Familiarity with the range of potential entities and any distinguishing features should prove valuable to thoracic radiologists, pulmonologists, and cardiothoracic surgeons when encountering the myriad of tracheobronchial neoplasms in clinical practice. Attention is paid to any features that may help render a more specific diagnosis before pathologic confirmation. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Added prognostic value of molecular imaging parameters over proliferation index in typical lung carcinoid: an [18F]FDG PET/CT and SSTR imaging study

OBJECTIVE

This study was performed to evaluate the prognostic meaning of volumetric and semi-quantitative parameters measured using [18F]FDG PET/CT and somatostatin receptor (SSTR) imaging in patients with typical lung carcinoid (TC), and their relationship with proliferative index (Ki67).

METHODS

We retrospectively reviewed 67 patients (38-94 years old, mean: 69.7) with diagnosis of TC who underwent [18F]FDG PET/CT and/or SSTR scintigraphy/SPECT with [111In]DTPA-Octreotide plus contrast-enhanced CT (CECT) at staging evaluation. All patients had Ki67 measured and a follow-up (FU) of at least 1 year. SSTR density (SSTRd) was calculated as the percentage difference of tumor/non-tumor ratio at 4 and 24 h post-injection. At PET/CT, metabolic activity was measured using SUVmax and SUVratio; volumetric parameters included MTV and TLG of the primary tumor, measured using the threshold SUV41%. ROC analysis, discriminant analysis and Kaplan-Meier curves (KM) were performed.

RESULTS

11 patients died during FU. Disease stage (localized versus advanced), SUVratio, SUVmax, Ki67, MTV and TLG were significantly higher in non-survivors than in survivors. ROC curves resulted statistically significant for Ki67, SUVratio, SUVmax, MTV and TLG. On multivariate analysis, stage of disease and TLG were significant independent predictors of overall survival (OS). In KM curves, the combination of disease stage and TLG identified four groups with significantly different outcomes (p < 0.005). Metabolic activity (SUVmax and SUVratio) was confirmed as significant independent prognostic factor for OS also in patients with advanced disease, with the best AUC using SUVmax. In patients with advanced and localized disease, SSTRd proved to be the best imaging prognostic factor for progression and for disease-free survival (DFS), respectively. In localized disease, SSTRd 31.5% identified two subgroups of patients with significant different DFS distribution and in advanced disease, a high cutoff value (58.5%) was a significant predictor of adverse prognosis.

CONCLUSION

Volumetric and semi-quantitative parameters measured using [18F]FDG PET/CT and SSTR imaging combined with Ki67 may provide a reference for prognosis evaluation of patients with TC, to better stratify risk groups with the goal of developing individualized therapeutic strategies.

Rare pulmonary tumors and carcinoma mimickers; experience from an interventional radiology unit with radiologic-pathologic correlation-A pictoral essay

BACKGROUND

Although imaging findings along with patients' clinical history may give clue for the etiology of a pulmonary lesion, the differentiation of benign pulmonary lesions from lung cancer could be challenging.

OBJECTIVE

The aim of this review article was to increase the awareness of the carcinoma mimicking lung lesions.

METHODS

This paper was designed to illustrate rare pulmonary tumors and carcinoma mimickers with emphasis on radiologic-pathologic correlation. Pitfalls encountered on CT images and also false positivity of PET-CT scans were also presented.

CONCLUSION

Several benign pulmonary lesions may grow in size on follow-up and some may show pathologic FDG (18F-fluorodeoxyglucose) uptake, which makes them indistinguishable from lung carcinoma by imaging. In addition, some slow-growing malignant lesions, such as carcinoid, may be false-negative on PET/CT scans.

Surgical Resection for Pulmonary Carcinoid: Long-Term Results of Multicentric Study-The Importance of Pathological N Status, More Than We Thought

BACKGROUND

Histological subdivision into typical (TC) and atypical (AC) is crucial for treatment and prognosis of lung carcinoids but can be also very challenging, even for experts. In this study, we aimed to strengthen or reduce the prognostic value of several pathological, clinical, or per-operative factors some of which are still controversial.

METHODS

We retrospectively reviewed clinical records related to 195 patients affected by TC (159) or AC (36) surgically treated between 2000 and 2014, in three different centers. Survival and subtypes comparison analyses were performed to identify potential prognostic factors.

RESULTS

TCs showed a lower rate of nodal involvement than ACs (N0 = 94.9%; N1 = 1.9%; N2 = 3.2% in typical and N0 = 63.8%; N1 = 16.6%; N2 = 19.4% in atypical carcinoids, respectively, p < 0.0001). Long-term oncological results of resected carcinoids were significantly better in TCs than ACs with higher 5- and 10-year overall survival rates (97.2 and 88.2% vs. 77.9 and 68.2%, respectively; p = 0.001) and disease-free survival rates (98.2 and 90.3% in typical and 80.8 and 70.7% atypical carcinoids, respectively; p = 0.001). Risk factors analysis revealed that AC subtype [HR 4.33 (95% CI 1.72-8.03), p = 0.002], pathological nodal involvement [HR 3.05 (95% CI 1.77-5.26), p < 0.0001], and higher SUV_max [HR 4.33 (95% CI 1.03-7.18), p = 0.002] were independently and pejoratively associated with overall survival. Factors associated with a higher risk of recurrence were AC subtype [HR 6.13 (95% CI 1.13-18.86), p = 0.002]; nodal involvement [HR 5.48 (95% CI 2.85-10.51), p < 0.0001]; higher Ki67 expression level [HR 1.09 (95% CI 1.01-1.20), p = 0.047]; and SUV_max [HR 1.83 (95% CI 1.04-3.23), p = 0.035].

CONCLUSION

Surgery for lung carcinoids allows satisfactory oncological results which mainly depend on carcinoid subtype dichotomy, pathological nodal status, and SUV_max.

Pulmonary Neuroendocrine Tumors: Part I. Spectrum and Characteristics of Tumors

Pulmonary neuroendocrine tumors arise from Kulchitzky cells of the bronchial mucosa and include typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma, and small cell lung cancer. These tumors have a variable growth rate that determines their presentation and prognosis. Typical carcinoid has the lowest growth rate and better prognosis; in contrast, small cell lung cancer is an aggressive tumor with a very poor prognosis. Although there are some overlapping histologic features between these tumors, clinical, imaging, and immunohistochemical markers are useful in the differentiation of pulmonary neuroendocrine tumors. The treatment options differ on the basis of histologic characteristics. In this article, we aim to describe the spectrum of neuroendocrine tumors of the lung, except for small cell lung cancer, and their clinical, pathologic, and imaging findings, with a focus on treatment options.

18F-FDG PET/CT rarely provides additional information other than primary tumor detection in patients with pulmonary carcinoid tumors

AIM

The purpose of this study was to assess the contribution of (18)F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET)/Computed Tomography (CT) in detection and staging of pulmonary carcinoid tumors.

METHODS

A total of 22 patients with pulmonary carcinoid tumors (14 typical, 8 atypical) were reviewed in this retrospective study. PET/CT images of all patients were evaluated for primary tumor as well as metastatic regional lymph nodes, bone and other distant metastases. PET/CT positivity of primary tumors was determined by visual interpretation. Tumor size, SUVmax and Hounsfield Unit (HU) values of the tumors were used to test for differences between tumor groups (typical carcinoids and atypical carcinoids).

RESULTS

SUVmax of carcinoids ranged from 1.24 to 11.1 (mean, 5.0; median, 2.67). The mean largest diameter of primary tumors was 2.7 ± 1.3 cm, ranging from 1 to 5.5 cm. The overall sensitivity of FDG PET/CT for detection of pulmonary carcinoid tumors was 81.8%. Tumor size, SUVmax and Hounsfield Unit (HU) values of the atypical carcinoids were higher than those for typical carcinoids. However, the results were not statistically meaningful (P > 0.05). The sensitivity and specificity of FDG PET/CT in the detection of mediastinal and hilar lymph nodes metastases were 25% and 83% respectively. One patient had bone metastasis.

CONCLUSION

Although FDG PET/CT can be a useful tool for the detection of pulmonary carcinoid tumors and distant metastasis, it cannot discriminate typical carcinoids from atypical ones and absence of an FDG avid lesion cannot exclude pulmonary carcinoid tumors. Moreover, PET/CT is not a reliable tool in the staging of mediastinal and hilar lymph nodes especially for those patients with typical carcinoids.

Functional imaging evaluation in the detection, diagnosis, and histologic differentiation of pulmonary neuroendocrine tumors

Pulmonary neuroendocrine tumors (pNETs) have distinct pathologic characteristics. Typical carcinoids are indolent neoplasms with a good prognosis, whereas atypical carcinoids have a less indolent behavior. Both are optimally treated with complete surgical excision. More aggressive pNETs often present with local invasion, thoracic lymph nodal metastases, and distant spread. Patients may not be candidates for surgical resection and are treated with chemotherapy and/or radiation therapy. This article examines the potential role of functional imaging evaluation using (18)F FDG and somatostatin analogues labeled with (68)Ga DOTA-peptides in well-differentiated pNETs with particular attention to clinical and surgical implications.

Role of 68Ga-DOTATOC PET/CT in initial evaluation of patients with suspected bronchopulmonary carcinoid

PURPOSE

The objective of this study was to evaluate the role of (68)Ga-DOTATOC positron emission tomography (PET)/CT scan in patients with suspected pulmonary carcinoid tumour and to compare its results with (18)F-fluorodeoxyglucose (FDG) PET/CT scan.

METHODS

In this prospective study, 32 patients (age 34.22 ± 12.03 years; 53.1 % female) with clinical suspicion of bronchopulmonary carcinoid were evaluated with (68)Ga-DOTATOC PET/CT and (18)F-FDG PET/CT. The two imaging modalities were compared, considering the tissue diagnosis as the reference standard.

RESULTS

Based on the reference standard 26 cases were carcinoid tumours [21 typical carcinoids (TC) and 5 atypical carcinoids (AC)] and 6 cases were non-carcinoid tumours. The sensitivity, specificity and accuracy of (68)Ga-DOTATOC PET/CT in the diagnosis of pulmonary carcinoid tumour were 96.15, 100 and 96.87 % respectively, whereas those of (18)F-FDG PET/CT were 78.26, 11.1 and 59.37 % respectively. The maximum standardised uptake value (SUV max) of TC on (68)Ga-DOTATOC PET/CT scan ranged from 3.58 to 55, while that of AC ranged from 1.1 to 32.5. (18)F-FDG PET/CT was true-positive in all cases of AC and false-negative in eight cases of TC (sensitivity for TC 61.9 % and for AC 100 %).

CONCLUSION

(68)Ga-DOTATOC PET/CT is a useful imaging investigation for the evaluation of pulmonary carcinoids. (18)F-FDG PET/CT scan suffers from low sensitivity and specificity in differentiating the pulmonary carcinoids from other tumours.

Integrated FDG-PET/CT imaging is useful in the approach to carcinoid tumors of the lung

Background

Carcinoids enter the differential diagnosis of the solitary pulmonary nodule. Bronchial carcinoids have been traditionally considered as FDG-PET negative but recent studies have found an higher sensitivity of integrated FDG-PET/CT for the detection of these neoplasms. The purpose of this study was to investigate the value of integrated FDG-PET/CT for the evaluation of SPN suspected to be carcinoids.

Methods

All patients with pathologically proven bronchial carcinoids who had FDG-PET/CT scans between 2006 and 2012 have been retrospectively reviewed. PET/CT was performed with the same scanner and the same technique for all patients. The following data were retrieved: age, sex CT findings (side, location, size, shape, margins), SUVmax, type of operation, pathological findings (size and number of mitoses). Regarding PET findings, only SUVmax was considered, whereas the visual assessment was not undertaken. Carcinoids were defined as typical and atypical and as central and peripheral. The long-term follow-up was also recorded. The SUVmax was compared with the other clinical, radiological and pathological variables to find any significant difference or correlation.

Results

Twenty-five patients were retrieved, 24 typical and one atypical carcinoid, 21 peripheral and 4 central lesions. The mean diameter on CT-scan was 25.3 mm and the clinical size correlated well with the pathological size. Sixty percent of the tumors were ovoid and 68% had smooth margins. The mean SUVmax was 3.6 (range 1.4-12.9). All the lesions were completely resected. The regression analysis showed a direct correlation between the SUVmax and the tumor size (p = 0.004). No further correlations were found between the SUVmax and the other variables. None of the patients had recurrent disease or died during the follow-up.

Conclusions

Our study showed that FDG-PET/CT might be a useful tool in the evaluation of SPNs suspected to be bronchial carcinoids. When a solitary pulmonary nodule shows an ovoid/round shape and smooth margins on the CT scan and demonstrates an FDG uptake higher than that of the normal lung and with a SUVmax value >1-1.5, a carcinoid should be suspected. If benign lesions can be presumably excluded, surgical resection or at least a biopsy of the lesion is recommended.

Bronchogenic carcinoid tumours that are 18F-fluorodeoxyglucose avid on positron emission tomography

OBJECTIVES

Bronchogenic carcinoid tumours are widely cited as non-fluorodeoxyglucose (FDG) avid. However, three case reports of FDG-avid bronchogenic carcinoid tumours have been published, leading to speculation as to which clinicopathological factors may be associated with increased activity on FDG-positron emission tomography. We reviewed a series of cases from our institution and compared them with the available reports in the literature, to attempt to identify the factors associated with FDG avidity in bronchogenic carcinoids.

METHODS

We performed a single-institution retrospective review.

RESULTS

One patient was identified at our institution who had a typical carcinoid tumour with a standardized uptake value (SUV) of 26, oncocytic features on histology and positive staining for glucose transporter 1 (GLUT1). Three additional patients were identified in the literature with typical bronchogenic carcinoids with SUVs of 39, 38 and 33. Two of these tumours stained positive for GLUT1, and the remaining patient was not tested. Two of these patients had oncocytic features on histology, and results on the remaining patient are not reported. Additionally, 4 patients at our institution were identified with bronchogenic carcinoids with average SUV of 2.6. All were GLUT1 negative, and none had oncocytic features. In the reported literature, excluding the four most FDG-avid tumours described above, atypical carcinoids had a higher mean SUV than typical carcinoids (5.7 vs 3.4, P = 0.02), but size was not correlated with SUV (r = 0.7, P = 0.3).

CONCLUSIONS

FDG uptake is commonly associated with worse prognosis in malignancy; however, bronchogenic carcinoids, particularly oncocytic typical carcinoids, are a possible source of extremely high SUVs on FDG-PET.

Somatostatin receptor scintigraphy with 111In-octreotide in pulmonary carcinoid tumours correlated with pathological and 18FDG PET/CT findings

PURPOSE

Pulmonary carcinoid (PC) tumors are rare neoplasms of the lung with good prognosis but diagnosis may be demanding since there is no exclusive modality alone to clearly differentiate a PC tumor. The purpose of this study is to establish the diagnostic features of somatostatin receptor scintigraphy (SRS), comparatively (where available) with 18FDG PET/CT (PET/CT) correlated with histopathologic findings.

METHODS

Twenty-one patients who underwent SRS with 111In-octreotide and were diagnosed as having PC tumors were retrospectively studied. Thirteen patients were performed PET/CT. Primary tumour size, Ki-67 indexes, image analysis data of SRS and PET/CT including maximum standardized uptake values (SUVmax) together with false negative, false positive, true positive and true negative lesions were documented and discussed.

RESULTS

Eleven (52.4%) patients were typical (TC) and 10 (47.6%) were atypical carcinoids (AC) with mean Ki-67 indexes of 2.1 and 24%, respectively. Patients underwent SRS for solitary pulmonary nodule (SPN) characterization (n = 12) and determination of disease extension (n = 9). Overall sensitivity and specificity of SRS in the detection of primary tumour, lymph nodes (LN) and distant metastasis (DM) were 76 and 97 %, respectively, whereas, positive and negative predictive values were 95 and 86 %. PET/CT was performed for determining disease spread (n = 3) and metabolic characterization (n = 10) of SPNs. Mean SUVmax in the primary pulmonary lesion in TCs and ACs were 2.9 ± 0.8 and 7.9 ± 5.4, respectively. Nodal involvement (n = 5) and DM (n = 3) were also detected. Sensitivity and specificity of PET/CT in the detection of primary tumour, LNs and DM were 85 and 89.4 %, respectively.

CONCLUSION

SRS is useful in the diagnosis and monitoring of PC tumors when incorporated with 18FDG PET/CT as a primary staging tool particularly in the determination of disease spread.

Growth of a solitary pulmonary nodule after 6years diagnosed as oncocytic carcinoid tumour with a high 18-fluorodeoxyglucose (18F-FDG) uptake in positron emission tomography-computed tomography (PET-CT)

INTRODUCTION

Pulmonary carcinoid tumour is low-grade neuroendocrine malignancy that is seen 1%-2% of all lung neoplasms. Oncocytic carcinoid type is a rarely seen variant of pulmonary carcinoids. As carcinoid tumours have hypometabolic activity, they usually have lower 18-fluorodeoxyglucose (18F-FDG) uptake than expected for lung carcinoma on positron emission tomography (PET).

CASE REPORT

A 45-year-old non-smoking man had a stable solitary pulmonary nodule followed for 6years; the tumour remained the same size (1.5×2.4cm) during this period. The patient was admitted to the hospital with complaints of repetitive sneezing and rhinorrhoea. He also experienced flushing and bronchospasm. His chest X-ray revealed a minimal increase in the size of the solitary pulmonary nodule (2.0×2.8cm). In PET-computed tomography (CT), the parenchymal nodule in the anterior segment of the right lung had a standard uptake value of 38.0mg/mL, which was interpreted as a malignant nodule. He underwent fibre-optic bronchoscopy, but cytology showed no evidence of malignancy. Right upper and middle bilobectomy was performed, and a pulmonary carcinoid tumour with an oncocytic subgroup was diagnosed. The diagnosis of carcinoid syndrome was further confirmed by an elevated 24-h urinary excretion of 5-hydroxyindoleacetic acid.

CONCLUSION

We present a rare case of an oncocytic carcinoid tumour with an increase in the size of a solitary pulmonary nodule after 6years' follow-up. In addition, PET-CT showed a very high 18F-FDG uptake in this patient, which is an unexpected finding with a pulmonary carcinoid tumour.

[Diagnosis and therapy of bronchopulmonary carcinoid tumors]

支气管肺类癌是罕见的肺部肿瘤，总体生长缓慢、预后尚可。根据其临床特征往往可以推测支气管肺类癌的诊断和亚型并指导治疗。其中年轻、CT表现为中心型肿瘤且无肺门或纵隔淋巴结肿大的病例，典型类癌的可能性较大。此亚型远处转移几率小，在手术治疗前除胸增强CT外可以不进行其它的常规术前分期检查。中心型肿瘤临床怀疑纵隔淋巴结累及或周围型肿瘤临床怀疑肺门纵隔淋巴结累及的病例，可能为不典型类癌。此亚型应做全面术前评估和分期。累及纵隔淋巴结的不典型类癌预后相对较差，应行多学科积极治疗。支气管肺类癌虽然其生物学特性不活跃，但均为恶性肿瘤，放化疗效果差，手术切除是最主要的治疗手段。彻底切除肿瘤、最大限度保留正常的肺组织是此类肺肿瘤外科治疗的基本目标。

Evaluation of the role of [18F]FDG-PET/CT and [68Ga]DOTATOC-PET/CT in differentiating typical and atypical pulmonary carcinoids

Pulmonary carcinoids are histologically classified into typical and atypical. It is important to identify these preoperatively for treatment planning and prognosis. Structural imaging cannot conclusively differentiate between them. The aim of this study was to assess the possibility of differentiating the 2 variants using [¹⁸F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) and [⁶⁸Ga]1,4,7,10-tetraazacyclododecane-N^I–IIII-tetraacetic acid-(d)-Phe¹-Thy³-octreotide (DOTATOC)-PET/CT. The imaging results of 20 patients with pulmonary carcinoids (13 typical, 7 atypical) on [¹⁸F]FDG-PET/CT and [⁶⁸Ga]DOTATOC-PET/CT were assessed retrospectively. Six typical carcinoids failed to reveal significant uptake on [¹⁸F]FDG-PET/CT. All the atypical carcinoids revealed significant uptake on the [¹⁸F]FDG-PET/CT that was higher than that in typical carcinoids (standardized uptake value (SUV)_max, 2.9–8.4, P = 0.001). The SUV_max in typical carcinoids on [⁶⁸Ga]DOTATOC-PET/CT was significantly higher (SUV_max, 8.8–66) compared with atypical carcinoids (SUV_max, 1.1–18.5, P = 0.002). Ratios of SUV_max on [⁶⁸Ga]DOTATOC-PET/CT to that on [¹⁸F]FDG-PET/CT were significantly higher (P < 0.001) in typical carcinoids compared with atypical carcinoids. The different uptake patterns on [¹⁸F]FDG and [⁶⁸Ga]DOTATOC-PET/CT. and the ratio of SUV_max may be helpful in differentiating between typical and atypical carcinoids.

68Ga-DOTA-NOC: a new PET tracer for evaluating patients with bronchial carcinoid

BACKGROUND

Conventional imaging techniques [computed tomography (CT), ultrasound, magnetic resonance] and somatostatin receptor scintigraphy are often insufficient to make a conclusive diagnosis of bronchial carcinoid (BC). PET is commonly used for the assessment of lung cancer but 18F-fluorodeoxyglucose, the most frequently used PET tracer, presents a low sensitivity for the detection of neuroendocrine tumours (NETs). New PET radiopharmaceuticals such as 68Ga-DOTA peptides, which directly bind to somatostatin receptors and are usually expressed on NET cell surfaces, have been reported to be superior to both morphological and somatostatin receptor scintigraphy imaging for gastroenteropancreatic NETs. However, their role in BC has never been evaluated. Our aim is to evaluate the role of 68Ga-DOTA-NOC (68Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-Nal3-octreotide) PET for the assessment of BC patients.

METHODS

Ten patients with pathologically proven well-differentiated BC and one patient with highly suggestive CT images for BC were studied by 68Ga-DOTA-NOC PET/CT. PET findings were compared with clinical follow-up, pathology and contrast-enhanced CT findings.

RESULTS

68Ga-DOTA-NOC PET/CT detected at least one lesion in nine of 11 patients and was negative in two. PET/CT and contrast-enhanced CT were discordant in eight of 11 patients, whereas in only three patients both provided similar results. PET/CT detected a higher number of lesions in five patients and excluded malignancy at sites considered positive on CT in three of 11; follow-up confirmed PET/CT findings in all patients. In PET/CT-positive patients, the mean maximal standardized uptake value was 25.9 [4.4-60.5]. On a clinical basis, PET/CT provided additional information in nine of 11 patients leading to the changes in the clinical management of three of nine patients.

CONCLUSION

PET/CT with Ga-DOTA-NOC was useful in BC patients because it led to a better evaluation of the extent of the disease.

Tumors in the tracheobronchial tree: CT and FDG PET features

A variety of tumors, including primary malignant tumors, secondary malignant tumors, and benign tumors, can occur in the tracheobronchial tree. Primary malignant tumors commonly originate from the surface epithelium or the salivary glands, whereas most benign tumors arise from the mesenchymal tissue. At computed tomography (CT), primary malignant tumors manifest as a polypoid lesion, a focal sessile lesion, eccentric narrowing of the airway lumen, or circumferential wall thickening. At fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET), most squamous cell carcinomas show high uptake, whereas adenoid cystic carcinoma and mucoepidermoid carcinoma show variable uptake depending on the grade of differentiation. High-grade malignancies tend to show high and homogeneous uptake. Carcinoid tumors commonly show intense enhancement at contrast material-enhanced CT, which can be helpful in making the diagnosis, and usually have lower uptake at FDG PET than would be expected for a malignant tumor. Secondary malignant tumors occur as a result of either hematogenous metastasis or direct invasion by a malignancy from an adjacent structure. Their CT manifestations are similar to those of primary malignant tumors, with uptake at FDG PET depending primarily on the metabolic activity and degree of differentiation of the primary tumor. Among the benign tumors, hamartoma and lipoma can show characteristic CT findings such as "popcorn" calcification or internal fat. However, CT findings in most benign tumors are nonspecific. At FDG PET, benign tumors usually show little or no uptake and can be differentiated from malignant tumors. Knowledge of the characteristic CT and FDG PET findings of tracheobronchial tumors can aid in diagnosis and treatment planning.

Correlation between FDG uptake and glucose transporter type 1 expression in neuroendocrine tumors of the lung

Neuroendocrine (NE) lung tumors are subdivided into the following types; typical (TC) and atypical carcinoids (AC), large cell neuroendocrine carcinoma (LCNEC), and small cell lung carcinoma (SCLC). Moreover, the determinants of the FDG uptakes of NE lung tumors have not been elucidated. Thus, the aim of the present study was to investigate the relationships between FDG uptake and glucose transporter type 1 (Glut-1) expression in these NE tumors. Tissue-proven NE lung tumor patients (n=32; age, mean+/-S.D.=67.8+/-10 years; male:female=28:4) who had undergone F-18 FDG-PET before treatment were enrolled in this study. There were 1 TC, 3 AC, 5 LCNEC, and 23 SCLC patients. FDG uptakes were quantified using maximum standardized uptake values (maxSUV). Paraffin sections of tumor tissues were immunostained using anti-Glut-1 antibody (Neomarkers, 1:50). Levels of Glut-1 expression are presented as percentages of tumor cells positively immunostained (%Glut-1). Relations between FDG uptakes and Glut-1 expression were assessed using Pearson correlation analysis. The maxSUVs of all NE lung tumors ranged from 0.6 to 29.5 (mean+/-S.D.=7.7+/-5.4) and %Glut-1 expression ranged from 0 to 100% (18+/-24%). The maxSUVs of all NE lung tumors were found to be significantly correlated with %Glut-1 expression (r=0.6471, p=0.0001). By subgroup analysis, maxSUV was also found to be significantly correlated with %Glut-1 expression in SCLC (n=23, r=0.6189, p=0.0016). FDG uptake was found to be highly correlated with Glut-1 expression in NE lung tumors. This result suggests that Glut-1 plays a crucial role in determining FDG uptake in these tumors.

Spectrum of findings and usefulness of integrated PET/CT in patients with known or suspected neuroendocrine tumors of the lung

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) has been known to increase diagnostic accuracy in differentiating benign and malignant lung lesions and to improve identification of lymph node and extrathoracic metastasis in pulmonary neoplasms. In this review, the authors describe the spectrum of integrated PET/CT findings on neuroendocrine (NE) tumors of the lung. We also demonstrate the usefulness of this imaging modality in patients with known or suspected NE tumors of the lung.

The utility of fluorodeoxyglucose positron emission tomography in the evaluation of carcinoid tumors presenting as pulmonary nodules

BACKGROUND

Fluorodeoxyglucose positron emission tomography (FDG-PET) is sensitive for detection of neoplastic solitary pulmonary nodules but may have decreased sensitivity for detection of carcinoid tumors. Our purpose was to determine the sensitivity of FDG-PET to detect pulmonary carcinoid tumors.

METHODS

We performed a retrospective review of our institutional results regarding FDG-PET in the setting of thoracic carcinoid neoplasms. We identified 16 patients with a pathologic diagnosis of bronchial carcinoid who had an antecedent FDG-PET (from 2000 to 2004). All patients but one presented with pulmonary nodule(s).

RESULTS

Sixteen patients had a diagnosis of carcinoid tumor, typical in 11 patients and atypical in 5 patients. The mean greatest pathologic dimension was 2.08 cm (range, 1.0 to 8.3 cm). Overall positron emission tomography (PET) sensitivity was 75% (12 true-positive and 4 false-negative results). The mean (+/- SD) size of carcinoids with false-negative PET results was not significantly different from carcinoids with true-positive results (1.6 +/- 0.81 cm and 2.35 +/- 1.87 cm, p = 0.54). Fifteen of 16 patients were staged pathologically, and positive nodes were found in 2 of these patients. PET lymph node staging agreed with pathologic staging in one stage 4 patient with positive lymph nodes and distant metastasis, but PET results were false negative in the other patient who had N2 with micrometastatic disease; stage IIIA.

CONCLUSIONS

FDG-PET imaging is useful for evaluation of typical and atypical thoracic carcinoid tumors. Although overall PET sensitivity for detection of carcinoid tumors is somewhat reduced as compared to non-small cell lung cancer, it is much higher than prior reports suggest.

F-18 FDG PET/CT imaging of low-grade mucoepidermoid carcinoma of the bronchus

Mucoepidermoid carcinomas in the bronchial tree are extremely rare tumors. Such tumors are classified into low-grade and high-grade on the basis of histological criteria. Fluorine-18-fluorodeoxyglucose positron emission tomography (F-18 FDG PET) is a useful technique for the evaluation of pulmonary lesions; however, to our knowledge, F-18 FDG PET findings in mucoepidermoid carcinoma of the bronchus have been described in only a few cases. Identifiable focal F-18 FDG uptake has been reported in high-grade mucoepidermoid carcinoma, but it is unclear whether F-18 FDG accumulates in low-grade mucoepidermoid carcinoma. Here, we present the case of a 37-year-old woman, with pathologically proven low-grade mucoepidermoid carcinoma, who underwent high-resolution computed tomography (CT) and F-18 FDG PET/CT before treatment.

Integrated PET/CT of pulmonary neuroendocrine tumors: diagnostic and prognostic implications

OBJECTIVE

The purpose of this study was to describe retrospectively integrated PET/CT findings on pulmonary neuroendocrine tumors and to correlate the findings with prognosis.

MATERIALS AND METHODS

Between May 2003 and February 2005, 37 consecutively enrolled patients (33 men and four women; mean age, 60 years) with histopathologically proven pulmonary neuroendocrine tumors underwent 18F-FDG PET/CT after enhanced standalone CT. CT was used to analyze the morphologic features of the tumors and PET to measure maximum standardized uptake value (SUV). Maximum SUVs of carcinoid tumors, large-cell neuroendocrine carcinomas (LCNECs), and small-cell lung carcinomas (SCLCs) were compared, and maximum SUV and tumor stage and prognosis were correlated.

RESULTS

Four (two typical and two atypical) of the seven carcinoid tumors had no FDG uptake or less than mediastinal uptake. The maximum SUVs of primary tumors, in increasing order, were significantly different for carcinoids (mean, 4.0; median, 3.4), LCNECs (mean, 12.0; median, 10.7), and SCLCs (mean, 11.6; median, 11.7) (p = 0.006, Kruskal-Wallis test). There was no significant correlation between maximum SUV of the primary tumor and the tumor stages of carcinoids, LCNECs, or SCLCs (p = 0.08, Jonckheere-Terpstra test; p = 0.768, Mann-Whitney test). Results of receiver operating characteristics analysis showed a maximum SUV greater than 13.7 suggested a poor survival period in cases of LCNEC and SCLC.

CONCLUSION

The maximum SUVs of neuroendocrine tumors are significantly different for carcinoid tumors, LCNECs, and SCLCs, and a high maximum SUV suggests short survival of patients with LCNEC or SCLC.

Use of integrated FDG PET/CT imaging in pulmonary carcinoid tumours

BACKGROUND

Integrated positron emission tomography (PET)/computed tomography (CT) scanners have been recently introduced in the diagnostic work-up of suspected pulmonary malignancy and demonstrate encouraging results in the staging of nonsmall-cell lung cancer.

OBJECTIVE

To evaluate the usefulness of integrated FDG PET/CT in pulmonary carcinoid tumours.

SETTING

University hospital.

METHODS

We studied 13 patients (mean age +/- 1 SD, 57 +/- 11 years) with pulmonary carcinoid tumours. All patients demonstrated a single pulmonary lesion. Integrated PET/CT scan and surgical resection were performed in all patients.

RESULTS

The pulmonary lesion size ranged from 1.1 to 5.0 cm. Final histological diagnosis confirmed 12 typical and one atypical pulmonary carcinoid. Mean proliferation rate of the typical carcinoids was 1.7 +/- 1.4%. None of the patients had recurrent carcinoid disease or died during follow-up (864 +/- 218 days). Mean standardized uptake value (SUV) of (18)F-fluorodeoxyglucose (FDG) in typical carcinoids was 3.0 +/- 1.5 (range 1.2 - 6.6); SUV in the atypical carcinoid was remarkably high with a value of 8.5. The SUV was lower than 2.5 in 6 of 12 patients (50%). Mediastinal lymph node metastases or extrathoracic metastases were not detected in any patient.

CONCLUSIONS

(18)F-fluorodeoxyglucose PET/CT imaging improves accurate localization of metabolic activity and thus the interpretation of pulmonary lesions on CT. FDG uptake in pulmonary carcinoid tumours is often lower than expected for malignant tumours. Therefore, surgical resection or biopsy of lesions suspected to be carcinoids should be mandatory, even if they show no hypermetabolism on FDG PET images.

Neuroendocrine tumors of the lung: clinical, pathologic, and imaging findings

Neuroendocrine tumors of the lung arise from Kulchitzky cells of the bronchial mucosa and comprise typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma (LCNEC), and small cell lung cancer (SCLC). At histopathologic analysis, these tumors demonstrate a progressive increase in the number of mitotic figures per 10 high-power fields of viable tumor and in the extent of necrosis, with typical carcinoid having the lowest values and SCLC having the highest. Typical carcinoid is less aggressive than atypical carcinoid, although these tumors have similar gross pathologic and radiologic features; LCNEC has a prognosis between that of atypical carcinoid and that of SCLC. SCLC is the most aggressive pulmonary neuroendocrine tumor and has the most specific imaging feature: mediastinal or hilar lymphadenopathy. At CT, carcinoid tumors appear as a spherical or ovoid nodule or mass with a well-defined and slightly lobulated border. When nonspherical, the tumor is elongated with its long axis parallel to adjacent bronchi. Calcification or ossification is seen in up to 30% of cases. The CT findings of LCNEC are nonspecific and are similar to those of other non-small cell lung cancers. Although there are some overlapping features between these tumors, integration of the clinical and imaging features may be helpful in differentiation of pulmonary neuroendocrine tumors.