Ppgl 18f Fdg Pet Indication

---
name: ppgl-18f-fdg-pet-indication
description: This skill identifies when 18F-FDG PET is indicated for detecting metastatic pheochromocytoma/paraganglioma (PPGL), especially in patients with known SDHx pathogenic variants or negative 123I-MIBG scintigraphy. Clinical triggers include suspected metastatic PPGL with negative MIBG, evaluating PPGL with known SDHx variant, and assessing treatment response in metastatic PPGL.
---

# 18F-FDG PET Indication for Metastatic PPGL

## STEP 1 — Gather Information
Collect clinical suspicion of metastatic PPGL, recent 123I-MIBG scintigraphy results, SDHx genetic testing status, and any symptoms or prior imaging.

## STEP 2 — Rule In / Rule Out
If 123I-MIBG scintigraphy is negative OR a pathogenic SDHx variant is known, rule in for 18F-FDG PET consideration; otherwise, rule out (do not indicate 18F-FDG PET for metastatic detection).

## STEP 3 — Classify or Stratify
If SDHx variant present, prioritize 18F-FDG PET over MIBG; if no variant but MIBG negative, consider 18F-FDG PET as alternative imaging.

## STEP 4 — Decide
Order 18F-FDG PET/CT for whole-body evaluation to detect metastatic lesions and assess treatment response.

## Clinical Guardrails / Mimics / Pitfalls
Watch for false positives from brown adipose tissue uptake; 18F-FDG PET is not first-line (MIBG preferred initially); avoid use without prior biochemical confirmation of PPGL; avoid in pregnancy unless absolutely necessary; correlate PET findings with clinical and biochemical data to avoid overinterpretation.

## Concrete Clinical Example
A 45-year-old patient with SDHB pathogenic variant, prior adrenal PPGL resection, rising chromogranin A, and negative 123I-MIBG scintigraphy undergoes 18F-FDG PET/CT, revealing a lumbar vertebral metastasis.

**Source:** Japan Endocrine Society Clinical Practice Guideline for the Diagnosis and Management of Pheochromocytoma and Paraganglioma 2025, Japan Endocrine Society, 2025, doi:10.1507/endocrj.EJ25-0165