¹⁸ F-fluoro-deoxy-glucose focal uptake in very small pulmonary nodules: fact or artifact? Case reports

• Main Authors: Calcagni Maria, Taralli Silvia, Maggi Fabio, Rufini Vittoria, Treglia Giorgio, Leccisotti Lucia, Bonomo Lorenzo, Giordano Alessandro
• Format: Article
• Language: English
• Published: BMC 2012-04-01
• Series: World Journal of Surgical Oncology
• Subjects: PET-CT; ¹⁸ F-FDG focal uptake; Small pulmonary nodules
• Online Access: http://www.wjso.com/content/10/1/71

<p>Abstract</p> <p>Background</p> <p>¹⁸F-fluoro-deoxy-glucose (¹⁸ F-FDG) positron emission tomography integrated/combined with computed tomography (PET-CT) provides the best diagnostic results in the metabolic characterization of undetermined solid pulmonary nodules. The diagnostic performance of ¹⁸ F-FDG is similar for nodules measuring at least 1 cm and for larger masses, but few data exist for nodules smaller than 1 cm.</p> <p>Case presentation</p> <p>We report five cases of oncologic patients showing focal lung ¹⁸ F-FDG uptake on PET-CT in nodules smaller than 1 cm. We also discuss the most common causes of ¹⁸ F-FDG false-positive and false-negative results in the pulmonary parenchyma.</p> <p>In patient 1, contrast-enhanced CT performed 10 days before PET-CT did not show any abnormality in the site of uptake; in patient 2, high-resolution CT performed 1 month after PET showed a bronchiole filled with dense material interpreted as a mucoid impaction; in patient 3, contrast-enhanced CT performed 15 days before PET-CT did not identify any nodules; in patients 4 and 5, contrast-enhanced CT revealed a nodule smaller than 1 cm which could not be characterized. The ¹⁸ F-FDG uptake at follow-up confirmed the malignant nature of pulmonary nodules smaller than 1 cm which were undetectable, misinterpreted, not recognized or undetermined at contrast-enhanced CT.</p> <p>Conclusion</p> <p>In all five oncologic patients, ¹⁸ F-FDG was able to metabolically characterize as malignant those nodules smaller than 1 cm, underlining that: ¹⁸ F-FDG uptake is not only a function of tumor size but it is strongly related to the tumor biology; functional alterations may precede morphologic abnormalities. In the oncologic population, especially in higher-risk patients, PET can be performed even when the nodules are smaller than 1 cm, because it might give an earlier characterization and, sometimes, could guide in the identification of alterations missed on CT.</p>