FDG-PET/CT shows a standardised uptake value (SUV) of 2.5 in a pulmonary nodule. What is the correct interpretation regarding malignancy?
- A SUV of 2.5 is borderline; false positives include active granulomatous disease, and false negatives include well-differentiated/mucinous carcinomas ✓
- B SUV > 2.5 is diagnostic of malignancy
- C SUV < 3.0 reliably excludes malignancy
- D SUV has no role in characterising pulmonary nodules
Correct answer: A. SUV of 2.5 is borderline; false positives include active granulomatous disease, and false negatives include well-differentiated/mucinous carcinomas
Explanation
An SUV threshold of 2.5 has been used as a cut-off for FDG-PET in pulmonary nodule characterisation but is not diagnostic. False positives (elevated SUV in non-malignant lesions) include active granulomatous infection (tuberculosis, histoplasmosis, sarcoidosis), rheumatoid nodules, and carcinoid. False negatives (low SUV in malignancies) include well-differentiated adenocarcinoma, bronchioloalveolar carcinoma, carcinoid tumours, mucinous carcinomas, and small lesions (<8 mm) due to partial volume effect. PET/CT is most useful for indeterminate nodules 8–30 mm.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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