484 chapter 12 Table 7. Patient and lesion characteristics of cases with discordant MD and [18F]FDG-PET/CT results casea age (years) sex (M/F) US size (mm) cytology [18F]FDG avid SUVmax (g/cm3) MD result Histopathological diagnosis [18F]FDG-/MD+, malignant or borderline histopathology 1 65 F 15 FN no 2.5 NRAS (c.182A>G) PTC, spindle cell variant, 15 mm, pT1bb 2 47 F 35 AUS no 2.2 ETV6/NTRK3 fusion FVPTC, 32 mm, pT2N0M0c [18F]FDG-/MD+, benign 3 62 M 36 AUS no 0.7 EGFR (c.2270A>G) FA, 25 mm 4 41 F 10 FN no 2.0 DICER1 (c.5126A>G) FA, 12 mm 5 50 F 36 AUS no 2.5 PTEN (c.755_758delATAT) FA, 25 mm 6 61 F 43 AUS no 2.6 TERT (c.-124C>T) FA, 36 mm 7 34 F 47 AUS no 2.1 DICER1 (c.5126A>G) no surgery, unchanged after 37 months f/u 8 74 M 53 AUS no 3.2 PTEN (c.379G>A) no surgery, unchanged after 45 months f/u 9 63 F 46 AUS no 3.5 CDKN2A (c.167G>T) no surgery, unchanged after 50 months f/u [18F]FDG+/MD-, malignant or borderline histopathology 10 58 F 15 FN yes 2.1 NIFTP, 20 mm 11 75 F 24 AUS yes 12.2 RCI type CNA FT-UMP with oncocytic changes, 21 mm 12 50 F 41 FN yes 5.9 paraganglioma, 40 mm 13 52 F 29 AUS yes 3.4 PTC, 8 mm, pT1aN0M0 14 46 F 36 FN yes 3.9 FTC, 37 mm, pT2N0M0 AUS, atypia of undetermined significance; CNA, copy number alterations; [18F]FDG, 2-[18F]fluoro-2-deoxy-Dglucose; F, female; f/u, follow-up; FA, follicular adenoma; FN, follicular neoplasm; FT-UMP, follicular tumour of uncertain malignant potential; FTC, follicular thyroid carcinoma; FVPTC, follicular variant PTC; M, male; MD, molecular diagnostics; NIFTP, non-invasive follicular thyroid neoplasm with papillary-like nuclear features; PTC, papillary thyroid carcinoma; RCI type, reciprocal chromosomal imbalance; SUVmax, maximum standardized uptake value; US, ultrasound. a: case numbers correspond to case numbers in Supplementary Table 5. b: This 15-mm neoplasm was difficult to diagnose, with a differential diagnosis of PTC or FA. After review by multiple expert thyroid pathologists and MD, it was finally considered a PTC, spindle cell variant, pT1b. c: This was a 32-mm follicular neoplasm with an 8-mm solid component and large cystic component, with a differential diagnosis of follicular adenoma or FVPTC. Morphologically difficult to diagnose, it was considered a pT2N0M0 FVPTC only after an ETV6/NTRK3 fusion was found on additional MD performed during revision of the histopathology. Both [18F]FDG-PET false-negative cases were previously discussed in more detail [501].
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