Management of solitary pulmonary nodules: how do thoracic computed tomography and guided fine needle biopsy influence clinical decisions?

Cone beam CT-guided navigation bronchoscopy: a cost-effective alternative to CT-guided transthoracic biopsy for diagnosis of peripheral pulmonary nodules

Objectives

To determine if cone beam CT-guided navigation bronchoscopy (CBCT-NB) is a cost-effective diagnostic procedure in patients with a pulmonary nodule (PN) with an intermediate risk for lung cancer.

Materials and methods

Two decision analytical models were developed to compare the long-term costs, survival and quality of life. In the first model, CBCT-NB was compared with CT-guided transthoracic needle biopsy (TTNB) in TTNB eligible patients. In the second model, CBCT-NB was compared with direct treatment (without pathology proven lung cancer) in patients for whom TTNB is not suitable. Input data were gathered in-house, from literature and expert opinion. Effects were expressed in quality-adjusted life years (QALYs). Sensitivity analyses were used to assess uncertainty.

Results

CBCT-NB can be cost-effective in TTNB eligible patients with an incremental cost-effectiveness ratio of €18 416 in an expert setting. The probabilistic sensitivity analysis showed that in 69% and 90% of iterations CBCT-NB remained cost-effective assuming a willingness to pay (WTP) of €20 000 and €80 000 per QALY. CBCT-NB dominated in the treatment strategy in which TTNB is not suitable. The probabilistic sensitivity analysis showed that in 95% of iterations CBCT-NB remained the dominant strategy, and CBCT-NB remained cost-effective in 100% of iterations assuming a WTP limit of €20 000. In the comparison between CBCT NB and TTNB, the deterministic sensitivity analysis showed that the diagnostic properties and costs of both procedures have a large impact on the outcome.

Conclusions

CBCT-NB seems a cost-effective procedure when compared with TTNB and when compared with a direct treatment strategy in patients with an intermediate risk PN.

GOECP/SEOR radiotheraphy guidelines for non-small-cell lung cancer

Non-small cell lung cancer (NSCLC) is a heterogeneous disease accounting for approximately 85% of all lung cancers. Only 17% of patients are diagnosed at an early stage. Treatment is multidisciplinary and radiotherapy plays a key role in all stages of the disease. More than 50% of patients with NSCLC are treated with radiotherapy (curative-intent or palliative). Technological advances-including highly conformal radiotherapy techniques, new immobilization and respiratory control systems, and precision image verification systems-allow clinicians to individualize treatment to maximize tumor control while minimizing treatment-related toxicity. Novel therapeutic regimens such as moderate hypofractionation and advanced techniques such as stereotactic body radiotherapy (SBRT) have reduced the number of radiotherapy sessions. The integration of SBRT into routine clinical practice has radically altered treatment of early-stage disease. SBRT also plays an increasingly important role in oligometastatic disease. The aim of the present guidelines is to review the role of radiotherapy in the treatment of localized, locally-advanced, and metastatic NSCLC. We review the main radiotherapy techniques and clarify the role of radiotherapy in routine clinical practice. These guidelines are based on the best available evidence. The level and grade of evidence supporting each recommendation is provided.

Dynamic contrast-enhanced CT compared with positron emission tomography CT to characterise solitary pulmonary nodules: the SPUtNIk diagnostic accuracy study and economic modelling

BACKGROUND

Current pathways recommend positron emission tomography-computerised tomography for the characterisation of solitary pulmonary nodules. Dynamic contrast-enhanced computerised tomography may be a more cost-effective approach.

OBJECTIVES

To determine the diagnostic performances of dynamic contrast-enhanced computerised tomography and positron emission tomography-computerised tomography in the NHS for solitary pulmonary nodules. Systematic reviews and a health economic evaluation contributed to the decision-analytic modelling to assess the likely costs and health outcomes resulting from incorporation of dynamic contrast-enhanced computerised tomography into management strategies.

DESIGN

Multicentre comparative accuracy trial.

SETTING

Secondary or tertiary outpatient settings at 16 hospitals in the UK.

PARTICIPANTS

Participants with solitary pulmonary nodules of ≥ 8 mm and of ≤ 30 mm in size with no malignancy in the previous 2 years were included.

INTERVENTIONS

Baseline positron emission tomography-computerised tomography and dynamic contrast-enhanced computer tomography with 2 years' follow-up.

MAIN OUTCOME MEASURES

Primary outcome measures were sensitivity, specificity and diagnostic accuracy for positron emission tomography-computerised tomography and dynamic contrast-enhanced computerised tomography. Incremental cost-effectiveness ratios compared management strategies that used dynamic contrast-enhanced computerised tomography with management strategies that did not use dynamic contrast-enhanced computerised tomography.

RESULTS

A total of 380 patients were recruited (median age 69 years). Of 312 patients with matched dynamic contrast-enhanced computer tomography and positron emission tomography-computerised tomography examinations, 191 (61%) were cancer patients. The sensitivity, specificity and diagnostic accuracy for positron emission tomography-computerised tomography and dynamic contrast-enhanced computer tomography were 72.8% (95% confidence interval 66.1% to 78.6%), 81.8% (95% confidence interval 74.0% to 87.7%), 76.3% (95% confidence interval 71.3% to 80.7%) and 95.3% (95% confidence interval 91.3% to 97.5%), 29.8% (95% confidence interval 22.3% to 38.4%) and 69.9% (95% confidence interval 64.6% to 74.7%), respectively. Exploratory modelling showed that maximum standardised uptake values had the best diagnostic accuracy, with an area under the curve of 0.87, which increased to 0.90 if combined with dynamic contrast-enhanced computerised tomography peak enhancement. The economic analysis showed that, over 24 months, dynamic contrast-enhanced computerised tomography was less costly (£3305, 95% confidence interval £2952 to £3746) than positron emission tomography-computerised tomography (£4013, 95% confidence interval £3673 to £4498) or a strategy combining the two tests (£4058, 95% confidence interval £3702 to £4547). Positron emission tomography-computerised tomography led to more patients with malignant nodules being correctly managed, 0.44 on average (95% confidence interval 0.39 to 0.49), compared with 0.40 (95% confidence interval 0.35 to 0.45); using both tests further increased this (0.47, 95% confidence interval 0.42 to 0.51).

LIMITATIONS

The high prevalence of malignancy in nodules observed in this trial, compared with that observed in nodules identified within screening programmes, limits the generalisation of the current results to nodules identified by screening.

CONCLUSIONS

Findings from this research indicate that positron emission tomography-computerised tomography is more accurate than dynamic contrast-enhanced computerised tomography for the characterisation of solitary pulmonary nodules. A combination of maximum standardised uptake value and peak enhancement had the highest accuracy with a small increase in costs. Findings from this research also indicate that a combined positron emission tomography-dynamic contrast-enhanced computerised tomography approach with a slightly higher willingness to pay to avoid missing small cancers or to avoid a 'watch and wait' policy may be an approach to consider.

FUTURE WORK

Integration of the dynamic contrast-enhanced component into the positron emission tomography-computerised tomography examination and the feasibility of dynamic contrast-enhanced computerised tomography at lung screening for the characterisation of solitary pulmonary nodules should be explored, together with a lower radiation dose protocol.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42018112215 and CRD42019124299, and the trial is registered as ISRCTN30784948 and ClinicalTrials.gov NCT02013063.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 17. See the NIHR Journals Library website for further project information.

Nondiagnostic Percutaneous Transthoracic Needle Biopsy of Lung Lesions: A Multicenter Study of Malignancy Risk

Purpose To evaluate the malignancy risk of lung lesions that show nondiagnostic results at transthoracic needle biopsy (PTNB) of the lung and to identify any malignancy-associated risk factors in each nondiagnostic category. Materials and Methods In this retrospective study, 9384 initial PTNBs (9239 patients [mean age, 65 years; age range, 20-99 years] consisting of 5729 men [mean age, 66 years; age range, 20-99 years] and 3510 women [mean age, 63 years; age range, 20-94 years]) were performed in eight institutions between January 2010 and December 2014. PTNB results were categorized as diagnostic (malignant or specifically benign) or nondiagnostic (nonspecific benign pathologic findings, atypical cells, or insufficient specimen), and the proportion of final malignant diagnoses per nondiagnostic category was obtained. Malignancy-associated factors were determined by using multivariable analyses. Results Nondiagnostic results were present in 27.6% (2590 of 9384) of PTNBs. Proportions of final malignant diagnoses were 21.3% (339 of 1592) for nonspecific benignities, 90.1% (503 of 558) for atypical cells, and 46.6% (205 of 440) for insufficient specimens. In the nonspecific benign category, granulomatous inflammation (odds ratio [OR], 0.04; 95% confidence interval [CI]: 0.02, 0.12; P < .001), abscess (OR, 0.04; 95% CI: 0.01, 0.28; P = .001), and organizing pneumonia (OR, 0.05; 95% CI: 0.01, 0.23; P < .001) were demonstrated to be important factors negating malignancy. Atypical cells suspicious for malignancy were more associated with malignancy (OR, 6.3; 95% CI: 1.9, 21.0; P = .003) than were atypical cells of indeterminate malignancy. All 130 lesions with atypical cells suggestive of malignancy were finally malignant. Conclusion After nondiagnostic lung biopsies, lesions categorized as atypical cell lesions have a high likelihood of malignancy, with somewhat lower likelihood for lesions with insufficient specimens and nonspecific benign categories. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Elicker in this issue.

The Solitary Pulmonary Nodule

Due to the high etiological diversity and the potential for malignancy, pulmonary nodules represent a clinical challenge, becoming increasingly frequent as the number of CT examinations rises. The topic gains even more importance as clear evidence for the effectiveness of CT screening was provided by the National Lung Screening Trial (NLST). Yet, the results were tempered by the high false-positive rate and the requirement of performing further diagnostic procedures. The management of those detected solitary pulmonary nodules is currently based on the individuals' risk of developing lung cancer, the pulmonary nodule characteristics and the capability of diagnostic and therapeutic approaches.

Diagnosis and management of pulmonary nodules

There are an increased number of pulmonary nodules discovered on CT scan images in part due to those performed for lung cancer screening. Risk stratification and patient involvement is critical in determining management ranging from interval imaging to invasive biopsy or surgery. A definitive diagnosis requires tissue biopsy. The choice of a particular biopsy technique depends on the risks/benefits of the procedure, the diagnostic yield and local expertise. This review will focus on the evaluation and management of pulmonary nodules based on the Fleischner Society and American College of Chest Physician guidelines. There have been recent changes to both societies' recommendations for incidental detection of solid and subsolid nodules, risk stratification, imaging, minimally invasive diagnostic techniques and definitive surgical options.

Prospective randomised trial of endobronchial ultrasound-guide sheath versus computed tomography-guided percutaneous core biopsies for peripheral lung lesions

AIM

To determine diagnostic rate, complications and patient tolerability of endobronchial ultrasound-guide sheath (EBUS-GS) and computed tomography (CT)-guided percutaneous core biopsy for peripheral lung lesions.

METHODS

Lesions >1 cm diameter on CT were randomised to either EBUS-GS or CT-guided biopsy. Excluded were patients with severe chronic obstructive airway disease, lesions touching visceral pleura or hilum, and patients with symptoms needing bronchoscopic evaluation. Patients completed preprocedure and postprocedure questionnaires on tolerability.

RESULTS

Of 64 participants (mean lesion size 29 ± 16 mm), 57 completed the study. Diagnostic sensitivity was 67% for EBUS-GS and 78% for CT-guided biopsy (P = not significant). In those with negative results, in the EBUS group, nine had a CT-guided biopsy as a cross-over, seven of which were positive. In the CT group, four had cross-over EBUS-GS of which three were diagnostic. Sensitivity for malignancy was 17/23 for EBUS-GS (74%) and 23/26 (88%, P = not significant). For lesions <2 cm, CT-guided biopsy had a significantly better diagnostic yield (80% vs 50%, P = 0.05). In EBUS-GS cases, for lesions with an air bronchogram, sensitivity was 89%. Pneumothorax and intercostal catheter insertion occurred in three and two cases, respectively, for EBUS, and 10 and 3 cases for CT-guided biopsy (P = 0.02 for pneumothorax). Nine unexpected admissions occurred after CT-guided biopsy compared with three after EBUS-GS. Overall, tolerability was high for both groups; however three patients had moderate-to-severe pain after CT-guided biopsy.

CONCLUSIONS

In lesions <2 cm, CT-guided biopsy had higher yields; however, EBUS-GS had better tolerability and fewer complications.

Positron emission tomography-computed tomography in the management of lung cancer: An update

This communication presents an update on the current role of positron emission tomography-computed tomography (PET-CT) in the various clinical decision-making steps in lung carcinoma. The modality has been reported to be useful in characterizing solitary pulmonary nodules, improving lung cancer staging, especially for the detection of nodal and metastatic site involvement, guiding therapy, monitoring treatment response, and predicting outcome in non-small cell lung carcinoma (NSCLC). Its role has been more extensively evaluated in NSCLC than small cell lung carcinoma (SCLC). Limitations in FDG PET-CT are encountered in cases of tumor histotypes characterized by low glucose uptake (mucinous forms, bronchioalveolar carcinoma, neuroendocrine tumors), in the assessment of brain metastases (high physiologic 18F-FDG uptake in the brain) and in cases presenting with associated inflammation. The future potentials of newer PET tracers beyond FDG are enumerated. An evolving area is PET-guided assessment of targeted therapy (e.g., EGFR and EGFR tyrosine kinase overexpression) in tumors which have significant potential for drug development.

[Management of pulmonary masses by guided transthoracic fine needle biopsy under computed tomography. Contribution from the Pathology and Radiology Departments of the Percy Military Hospital (Clamart, France) over 10 years]

Examining 260 samples of pulmonary nodules obtained by percutaneous biopsy under tomodensitometric control from the departments of radiology and pathology over 10 years, the authors note the advantages and disadvantages of this technique, provide the results of their experience and emphasise the importance of these biopsies in malignant pathology. The results of this series can be superposed with those found in the literature. Malignant tumours account for 75 % of the cases, with a clear prevalence of primitive adenocarcinoma. Benign pathology (approximately, 14 % of the cases) was represented by necrosis without any specificity, fibrous reaction and infectious causes. The act had to be repeated for the false negatives (7 %).

Number of biopsies in diagnosing pulmonary nodules

Purpose:

To determine the number of specimens to be obtained from pulmonary lesions to get the highest possible accuracy in histological work-up.

Materials and methods:

A retrospective evaluation (January 1999 to April 2004) covered 260 patients with thoracic lesions who underwent computer tomography (CT)-guided core-cut biopsy in coaxial technique. All biopsies were performed utilizing a 19 gauge introducer needle and a 20 gauge core-cut biopsy needle. In all, 669 usable biopsies were taken (from 1–5 biopsies in each setting). The specimens were marked sequentially and each biopsy was worked up histologicaly. The biopsy results were correlated to histology after surgery, clinical follow-up or autopsy. The number of biopsies was determined that is necessary to achieve the highest possible accuracy in diagnosing pulmonary lesions.

Results:

In 591 of 669 biopsies (88.3%), there were correct positive results. The overall accuracy was 87.4%. In 193 of 260 (74.2%) patients, a suspected malignancy was confirmed. In 50 of 260 (19.2%) patients, a benign lesion was correctly diagnosed. Seventeen (6.5%) patients were lost to follow-up. The first, second and third biopsies had cumulative accuracies of 63.6%, 89.2% and 91.5%, respectively (P < 0.02). More biopsies did not show any higher impact on accuracy.

Conclusion:

For the highest possible accuracy in diagnosing pulmonary lesions by CT-guided core-cut biopsy, at least three usable specimens are recommended to be taken.

Prediction of true positive lung cancers in individuals with abnormal suspicious chest radiographs: a prostate, lung, colorectal, and ovarian cancer screening trial study

INTRODUCTION

Chest radiographs are routinely employed in clinical practice. Radiographic findings that are abnormal suspicious (AS) for lung cancer occur commonly. The majority of AS radiographic abnormalities are not cancer. This study identifies predictors of true positive (TP) AS and presents models for estimating the probability of lung cancer.

METHODS

This is a prospective cohort study nested in the randomized National Cancer Institute's Prostate Lung Colorectal Ovarian Cancer Screening Trial (PLCO). First-time AS screens in the screening arm of the PLCO were studied. Associations between nonradiographic and radiographic factors, and TP AS were evaluated by multiple logistic regression.

RESULTS

The PLCO intervention arm had 77,465 individuals, of whom 12,314 were AS and of these 232 (1.9%) had lung cancer (were TP). Important independent predictors of TP were older age, lower education, greater pack years and duration smoking history, body mass index <30, family history of lung cancer, lung nodule, lung mass, unilateral mediastinal or hilar lymphadenopathy, lung infiltrate, and upper/middle chest AS location. The model including these variables had a receiver operator characteristic area under the curve (ROC AUC) of 86.4%. This model excluding the smoking variables had an ROC AUC of 77.1% and excluding all nonradiographic variables had an ROC AUC of 73.3% (p < 0.0001 for all these model differences). Smoking and nonsmoking nonradiographic variables significantly added to prediction.

CONCLUSION

This study identifies important nonradiographic and radiographic predictors of lung cancer, and presents an accurate model for estimating the probability of lung cancer in individuals with suspicious radiographs. These findings may be of value for screening, research, and patient and clinician decision-making.

Computed tomography-navigated transthoracic core biopsy of pulmonary lesions: which factors affect diagnostic yield and complication rates?

RATIONALE AND OBJECTIVES

Only a few studies have systematically evaluated risk factors for pneumothorax and pulmonary hemorrhage in computed tomographically (CT)-guided transthoracic lung biopsy (TLB). We evaluated the diagnostic yield of CT-guided TLB and determined risk factors for pneumothorax and hemorrhage.

METHODS

One hundred seventy-two CT-guided TLBs were performed on 159 patients (mean age 66 +/- 11 years; 72% male) using a 16-gauge core biopsy needle. Lesion and patient characteristics, lung function analysis, CT signs of emphysema, histopathologic diagnoses, and complications were recorded. Statistical analysis was performed with multivariate regression analysis.

RESULTS

Histopathologic diagnosis was established in 153 cases (89%). Although lesion size was higher (47 +/- 29 vs. 43 +/- 35 mm, P = .191) and depth was lower (22 +/- 23 vs. 6 +/- 23 mm, P = .350) in procedures with histopathologic diagnosis, no parameter showed significant impact on diagnostic yield. Sensitivity and specificity for detection of malignancy were 93% and 100%, respectively, whereas positive and negative predictive values were 100% and 88%. Overall accuracy was 95%. Pneumothorax occurred in 45 procedures (26%). Hemorrhage was recorded in 17 procedures (10%). There was higher frequency of pneumothorax in smaller lesions (35 +/- 23 vs. 50 +/- 31 mm, P = .003; odds ratio = .96) and greater depth (29 +/- 29 vs. 20 +/- 19 mm, P = .05; odds ratio = 1.03). CT signs of emphysema revealed higher incidence of hemorrhage (35% vs. 23%; P = .04; odds ratio=41.03). Other parameters were nonsignificant.

CONCLUSIONS

The high diagnostic yield of CT-guided TLB was not affected by lesion characteristics or emphysema. Pneumothorax rate was influenced by lesion size and depth. Hemorrhage was associated with CT signs of emphysema.

Neodymium:yttrium-aluminium-garnet laser for excision of pulmonary nodules: an institutional review

Eighty patients amongst 850 undergoing pulmonary surgery with the use of neodymium:yttrium-aluminium-garnet (Nd:YAG) laser had a solitary pulmonary nodule (< or = 50 mm) on chest radiography, which was confirmed or suspected pre-operatively to be primary lung cancer. All patients had a mini-thoracotomy to expose the lesion. They then had Nd:YAG laser to excise the nodule locally. There was no hospital mortality. Six patients had non-fatal post-operative complications. Pathologically, 46 patients had primary lung cancer and ten had secondary lung cancer. Twenty-four others had benign lesions. Mean hospital stay was 5.5 days. Post-operative reduction of forced vital capacity (FVC) and forced expiratory volume in one second (FEV(1)) was 14% and 13% (mean), respectively. Thirty-seven patients with primary lung cancer were followed up for between 12 months and 60 months. Mean survival time of these patients was 39 months (s.d. 13 months). It was concluded that Nd:YAG laser for pulmonary nodular lesions should be considered for a selected group of patients unsuitable for standard resection.

Intrathoracoscopic localization techniques

BACKGROUND

Several techniques for localizing pulmonary nodules have been described, but the advantages and disadvantages of each method remain unclear. We reviewed ultrasound, endofinger, finger palpation and wait and watch, radioguided, vital dye, fluoroscopic, agar marking, and needle wire methods for localizing pulmonary nodules.

METHODS

Original, peer-reviewed, and full-length articles in English were searched with PubMed and ISI Web of Sciences. Case reports and case series with less than 10 patients were excluded.

RESULTS

All localization techniques showed good reliability, but some carry a high rate of major or minor complications and drawbacks.

CONCLUSION

No ideal localization technique is available; thus, the choice still depends on surgeon's preference and local availability of both specialists and instruments.

Repeat needle biopsies combined with clinical observation are safe and accurate in the management of a solitary pulmonary nodule

BACKGROUND

Sixty percent of removed solitary pulmonary nodules (SPNs) are benign. An approach that reduces the unnecessary excision of benign nodules is consistent with the oncologic objective of organ preservation.

METHODS

A prospective observational study was performed at a lung cancer referral center in which consecutive patients were evaluated who presented with SPNs measuring < 4 cm on computed tomography (CT) scans. Patients underwent transbronchial biopsy (TBB), percutaneous needle aspiration (PCNA), clinical observation, repeat CT scans, and repeat biopsies. Patients were observed clinically and underwent repeat biopsies in an effort to reduce unnecessary surgical intervention.

RESULTS

One hundred eighteen patients underwent 194 biopsy sessions, including 137 TBB sessions and 57 PCNA sessions. The mean follow-up was 4 years. The shortest follow-up of a benign lesion was 3 years. The incidence of malignancy was 61%. The positive predictive value, negative predictive value, sensitivity, specificity, and accuracy all were 100%. Five patients had a delayed change in diagnosis from benign to malignant. This delay in diagnosis neither resulted in a change in tumor stage nor had an impact on patient management or survival.

CONCLUSIONS

Repeat needle biopsies combined with clinical observation and repeat CT scans can classify an SPN as benign versus malignant with 100% accuracy (95% confidence interval, 96.1-100.0%). An SPN diagnostic approach that includes a TBB, then PCNA, clinical observation, repeat CT scans, and repeat biopsies for continued suspicion of malignancy appears to reduce the unnecessary surgical excision of benign nodules from the current rate of 60% to 5% of SPN resections without affecting the survival of patients who have malignant SPNs.

Management strategies for the solitary pulmonary nodule

PURPOSE OF REVIEW

The challenge of diagnosis and management of solitary pulmonary nodules is among the most common yet most important areas of pulmonary medicine. Ideally, the goal of diagnosis and management is to promptly bring to surgery all patients with operable malignant nodules while avoiding unnecessary thoracotomy in patients with benign disease.

RECENT FINDINGS

Effective management of the solitary pulmonary nodule depends upon an understanding of decision analysis principles so that diverse technologies can be integrated into a systematic approach.

SUMMARY

In almost all patients computed tomography (CT) is the best first step. Three key questions can then help guide the workup of the SPN. These are what is the pretest probability of cancer, what is the risk of surgical complications, and does the appearance of the nodule on CT scan suggest a benign or malignant etiology. In patients with average surgical risk, positron emission tomography (PET) scan is warranted when there is discordance between pretest probability of cancer and the appearance of the nodule on CT scan. Thus, when either the patient has a low risk of cancer and the CT suggests a malignant origin, or when there is high risk of cancer and the CT appears benign, PET scan will be cost effective. In most other situations, PET scanning is only marginally more effective than CT and fine needle aspiration strategies but costs much more.

The performance of( 18)F-fluorodeoxyglucose positron emission tomography in small solitary pulmonary nodules

Solitary pulmonary nodule (SPN, intraparenchymal lung mass <3 cm) is often a diagnostic challenge. This study was performed to evaluate the diagnostic accuracy of( 18)F-fluorodeoxyglucose positron emission tomography (FDG PET) in radiologically indeterminate SPN < or =10 mm on spiral CT. Between August 1997 and March 2001, we identified all patients with radiologically indeterminate SPNs < or =10 mm who were referred for FDG PET imaging at the VU University Medical Centre. All PET scans were retrospectively reviewed by an experienced nuclear medicine physician. PET was considered positive in cases with at least moderately enhanced focal uptake, and otherwise as negative. Lesions were considered benign on the basis of histology, no growth during 1.5 years or disappearance within at least 6 months. Thirty-five patients with 36 SPNs < or =10 mm in diameter at clinical presentation were identified (one patient had two metachronous lesions). In 13 of 14 malignant nodules and in two of 22 benign nodules, diagnosis was confirmed by histology. Prevalence of malignancy was 39%. PET imaging correctly identified 30 of 36 small lesions. One lesion proved to be false negative on PET (CT: 10 mm), and in five lesions, PET scans proved to be false positive. Specificity was 77% (17/22; 95% CI: 0.55-0.92), sensitivity 93% (13/14; 95% CI: 0.66-1.0), positive predictive value 72% (13/18; 95% CI: 0.46-0.90) and negative predictive value 94% (17/18; 95% CI: 0.73-1.0). This retrospective study suggests that FDG PET imaging could be a useful tool in differentiating benign from malignant SPNs < or =10 mm in diameter at clinical presentation. Such results may help in the design of larger prospective trials with structured clinical work-up.