PET/CT in Mediastinal Lymphadenopathy; Merits and Pitfalls

Abstract

Background: Enlarged mediastinal lymph nodes require assessment to ascertain their benign or malignant origin. Noninvasive techniques are crucial for diagnosing benign as well as malignant mediastinal lymph nodes. PET/CT, which combines morphological plus functional imaging, is a noninvasive technique utilized for evaluating mediastinal lymphadenopathy. In PET, the standard uptake value (SUV), as a semi-quantitative measure, indicates the level of metabolic activity in certain tissues. While FDG absorption levels are typically elevated in neoplastic conditions, they may also be attributed to physiological factors or artifacts. Furthermore, FDG uptake may manifest in benign diseases, including viral, inflammatory, as well as iatrogenic lesions.

Results: This cross-sectional study included 120 cases; 67 male (56 %) and 53 female (44 %). 63 cases (52.5%) presented with mediastinal lymphadenopathy on CT and 57 patients (47.5%) came for metastatic work up. They were between the ages of 23 and 85, with 62 being the mean age. Three patients showed high FDG uptake suggesting malignant diagnosis, however, was to be benign. Thirty-four patients showed low FDG uptake, suggesting benign lesions yet with malignant final diagnosis, while thirty patients showed borderline FDG uptake so being indeterminate diagnosis. One patient showed metabolic activity of undetermined nature and proved finally as benign nature. All of these findings were considered as pitfalls for using PET/CT examination in assessment of the malignant, benign and metabolically active lesions.

Conclusions: PET/CT examination merits; detection of primary lesions and metastasis, assessment of treatment response and being useful as non-invasive investigation for follow up. On the other hand, number of patients showed high FDG uptake suggesting malignant diagnosis, however, was to be benign, and others showed low FDG uptake, suggesting benign lesions yet with malignant final diagnosis, others showed borderline FDG uptake so being indeterminate diagnosis. Ultimately, implementing both PET FDG uptake and CT characteristics, such as size and attenuation, in a comprehensive integrated report, alongside high-quality clinical and laboratory data in a multidisciplinary meeting context, enhances the likelihood of achieving an accurate diagnosis for the patient.