Progressing Sclerosing Mesenteritis (Mesenteric Panniculitis) Mimics Progression of Malignancy After Neoadjuvant Chemotherapy for Gastric Adenocarcinoma on Serial 18F-FDG PET/CT

Acute Findings on FDG PET/CT: Key Imaging Features and How to Differentiate Them from Malignancy

PURPOSE OF REVIEW

To review acute findings commonly encountered during routine clinical FDG PET/CT studies and present key imaging features to differentiate them from malignant counterparts.

RECENT FINDINGS

FDG PET/CT is extensively used in routine clinical practice for oncology patients. Incidental acute findings in patients undergoing FDG PET/CT are increasingly common, and awareness of these findings and their mimics are important in delivering a clinically relevant and accurate radiological report for directing further management.

SUMMARY

This article will review examples of common acute findings encountered during routine FDG PET/CT scans, compare them against examples of FDG-avid malignancy that can mimic these findings and emphasize key imaging findings to differentiate acute findings from their malignant mimics.

18F-FDG PET/CT Imaging of Peritoneal Fibrosis Mimicking Persistent Metastatic Ovarian Carcinoma

A 65-year-old woman was addressed for clinical and biological suspicion of ovarian cancer relapse. ¹⁸F-FDG PET/CT revealed massive peritoneal carcinomatosis. Post-chemotherapy PET/CT showed complete metabolic response in initial localizations albeit three new ¹⁸F-FDG uptakes appeared in the mesentery and in the retro-hepatic space. Close follow-up (including PET/CT scan) and surgical examination of the abdominal cavity confirmed the absence of malignancy and the benign nature of these lesions, which appeared to be peritoneal fibrosis mimicking persistent carcinomatosis.

Mesenteric panniculitis mimicking early recurrence at end-of-treatment evaluation in malignant lymphoma: Differentiation by active surveillance with F-18 FDG PET/CT imaging

Mesenteric panniculitis is a relatively rare fibro-inflammatory condition of the mesentery. In acute phase, it demonstrates avid uptake on Fluorine-18 FDG PET/CT (PET/CT). Thorough assessment is needed to differentiate from viable or recurrent disease in patients with malignant lymphoma because it mimics active lymphomatous disease on PET/CT. In this article, 3 illustrative cases of malignant lymphoma are presented. PET/CT demonstrated new FDG-avid mesenteric lesions at the end-of-treatment evaluation while the original disease showed significant response. Early recurrence was initially suspected, but together with clinical course and findings, active surveillance was opted. Sequential follow-up PET/CTs showed various patterns of metabolic activity over time; it can persist for months or more, or metabolic activity can fluctuate over time. Eventually benignity was confirmed in these cases. These cases underscore the importance of interpretation with clinical context and awareness of chronological metabolic changes of mesenteric panniculitis to determine proper management.