Focal and Diffuse FDG Uptake Patterns of Endotracheal Lymphoma

Unexpected focal fluorodeoxyglucose uptake in main organs; pass through or pass by?

Since the inception of fluorine-18 fluorodeoxyglucose (F-18 FDG), positron emission tomography/computed tomography (PET/CT) utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology, with global prevalence in clinical practice. Given that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh, the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not uncommon. Numerous investigations have been undertaken to delineate the distinctive features of these findings, yet the outcomes have proven inconclusive. The incongruent results of these studies present a challenge for physicians, leaving them uncertain about the appropriate course of action. This article provides a succinct overview of the characteristics of fluorodeoxyglucose, followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative organs. In conclusion, while the prevalence of unrecognized malignancy varies across organs, malignancies account for a substantial proportion, ranging from approximately one-third to over half, of incidental focal uptake. In light of these rates, physicians are urged to exercise vigilance in not disregarding unexpected uptake, facilitating more assured clinical decisions, and advocating for further active evaluation.

Primary Pancreatic Lymphoma on FDG PET/CT

A 69-year-old man underwent FDG PET/CT to evaluate a right upper abdominal mass. The images showed peripherally increased activity with central photopenic region in the head of the pancreas, which was consistent with pancreatic malignancy. Histopathologic findings showed characteristic findings of diffuse large B-cell lymphoma. The activity was diminished on follow-up PET/CT after 8 courses of chemotherapy.

Endotracheal Leiomyoma Mimicking Malignancy on 18F-FDG PET/CT in a Patient With Papillary Thyroid Carcinoma

Endotracheal leiomyoma is a rare benign lesion, accounting for approximately 1% of tracheal tumors, and generally occurs in the lower respiratory tract. Because its growth causes airway obstruction symptom, surgical treatment is generally suggested after detection. We report a case with leiomyoma of the cervical endotracheal space showing intense FDG uptake on F-FDG PET/CT mimicking malignancy in a 79-year-old woman with papillary thyroid carcinoma.