Fig. 6.
True negative evaluation with combined PET/DWIMRI (discordant findings on MRI, DWI and PET). A 77-year-old male with pain and neck fistula 5 years after total laryngectomy and radiotherapy for squamous cell carcinoma of the larynx. T2 (A): neopharynx with intermediate signal (oblique arrows) suggesting probable recurrence and fistula connecting the neopharynx to the skin (vertical arrow). Surrounding long-standing fibrosis with strong T2 hypointensity (asterisk). White arrowhead: occluded common carotid artery (CCA). Grey arrowhead: left normal CCA. (B) DWI with b1000 (left) and ADC map (right): absent restriction of diffusion in the neopharynx (arrows) and along the fistulous tract (ADCmean = 1.578–1.692 × 10-3 mm2/s). Area of fibrosis (asterisk). Occluded right CCA (arrowhead). (C) PET/MRI (PET fused with gadolinium-enhanced Dixon): probable recurrence with high FDG uptake (arrows, SUVmean = 5.357; SUVmax = 6.979). Radiation-induced arteriopathy (FDG uptake, arrowheads). As MRI, DWI and PET evaluations were discordant, the case was considered as probably negative for recurrence. Surgical biopsies revealed granulation tissue in the neopharynx and fibrosis around the fistula. (D) Histological section (HE, original magnification 200×, left image): fibrosis with rare fibroblasts. Polarised light (right image, original magnification 100×): thick birefringent collagen bundles. Follow-up of 36 months further confirmed absence of recurrence