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Ann Thorac Surg 2005;79:989
© 2005 The Society of Thoracic Surgeons

INVITED COMMENTARY

Leuven Lung Cancer Group, Department of Thoracic Surgery, University Hospital Gasthuisberg, Catholic University, Herestraat 49, B-3000 Leuven, Belgium

(E-mail: paul.deleyn{at}uz.kuleuven.ac.be).

A solitary pulmonary nodule remains a diagnostic challenge in daily practice. Positron emission tomography (PET) with 18F-2-fluoro-2-deoxy-glucose (FDG) has been studied extensively in the evaluation of the indeterminate pulmonary nodule. As shown by a large meta-analysis, the sensitivity to detect malignancy is 96.8% with a specificity of 77.8% [1]. Potential pitfalls in sensitivity are due to the fact that a critical mass of metabolically active malignant cells is required for PET diagnosis. It is well-known that false negative findings occur in lesions less than 1 cm. Due to these good results obtained with PET scan, some centers will reassure patients with nodules greater than 1 cm that are negative or faintly positive on PET scan and these patients will be monitored by serial radiologic or PET examinations. However, some types of tumors (bronchiolo-alveolar cell carcinoma) may have a negative PET scan due to low metabolic activity related to a significant lower Glut-1 expression (the main transporter enzyme needed for FDG uptake) [2].

In the multitude of published reports on the use of PET in pulmonary nodules, the series of Nomori and colleagues in this issue of The Annals of Thoracic Surgery is of particular importance. This series shows that even in nodules greater than 1 cm, PET scan is negative or faintly positive in a significant proportion of patients with well-differentiated adenocarcinoma. Their study included 33 patients with well-differentiated adenocarcinomas larger than 1 cm. The PET scan was negative in 18 patients (55.6%). In 8 patients (24.2%), PET scan was faintly positive. However, in faintly positive findings, using the contrast ratio to the contralateral lung and contrast ratio to the cerebellum did result in a significantly higher sensitivity. Only in 7 patients (21.2%) was the PET scan definitely positive. The PET scan was always true positive in squamous cell, large cell, and small cell carcinomas. Furthermore, this study shows that there is no difference in sensitivity and specificity between visual assessment and using standardized uptake value.

As the authors conclude, in PET negative nodules the appearance of the lesion on spiral computed tomography (CT) is of critical importance. In another article [3], the same authors showed that, in nodules ranging between 10 and 30 mm FDG, PET correctly detected 55 of 59 (93%) of malignant nodules with a solid aspect on CT, while it was positive in only 1 out of the 10 malignant nodules with a faint or ground glass aspect on CT. Faint or ground glass opacities have become a well-known entity on spiral CT and can be ascribed to either focal pneumonia or interstitial inflammation, premalignant atypical adenoma hyperplasia, and malignant bronchiolo-alveolar cell carcinoma. Correct diagnosis of these truly early types of lung cancer is vital since they carry an excellent prognosis after resection. The appearance of a lesion on CT can necessitate biopsy or resection even when the PET scan is negative.

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1. Gould MK, Maclean CC, Kuschner WG, Rydzak CE, Owens DK. Accuracy of positron emission tomography for diagnosis of pulmonary nodules and mass lesions JAMA 2001;285:914-924.[Abstract/Free Full Text]
2. Higashi K, Ueda Y, Sakurai A, et al. Corrrelation of Glut-1 glucose transporter expression with {18}FDG uptake in non-small cell lung cancer Eur J Nucl Med 2001;27:1778-1785.
3. Nomori H, Watanabe K, Ohtsuka T, Naruke T, Suemasu K, Uno K. Evaluation of F-18 fluorodeoxyglucose (FDG) PET scanning for pulmonary nodules less than 3 cm in diameter, with special reference to the CT images Lung Cancer 2004;45:19-27.[Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Paul De Leyn Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by De Leyn, P. Search for Related Content PubMed Articles by De Leyn, P. Related Collections Lung - cancer Related Article