Rabbit fever: granulomatous inflammation by Francisella tularensis mimics lung cancer in dual tracer ¹⁸FDG and ⁶⁸Ga-FAPI PET/CT

Excerpt

A 39-year-old hunter presented with chills, headache, limb pain, tachycardia, hypertension, ventricular extrasystoles, elevated inflammatory values, and persistent chest pain. A CT scan revealed a mass on the left hilus (A). Due to suspicion of lymphoma or lung cancer 1 week later, an ¹⁸FDG (B–D) plus a ⁶⁸Ga-labeled fibroblast activation protein inhibitor (⁶⁸Ga-FAPI) PET/CT scan (E–G) were performed. The hilar mass increased in size (B, E) and demonstrated both intense ¹⁸FDG uptake (SUVmax 24.5) (C, D) and ⁶⁸ Ga-FAPI accumulation (SUVmax 23.2) (F, G) strongly indicating malignancy. However, subsequent EBUS-TBNA and EUS-B yielded necrotizing granulomatosis (H). Finally, a bone-hard mass on the left hilus discharging creamy pus was resected by VATS. Pathological and microbiological workup evidenced Francisella tularensis infection by FISHseq analysis (Fluorescence in situ hybridization combined with 16S rRNA gene amplification and sequencing [1]), ELISA, and Western blot. Postoperative bronchoscopy demonstrated re-established bronchus patency (I). After antibiotic therapy with gentamicin and ciprofloxacin, no recurrence was detectable on CT control 20 weeks later (J). …