PMC9807755_01
(A) FDG-PET MIP: initial staging, (B) FDG-PET MIP: left adrenal relapse, arrow, and (C) FDG-PET MIP: complete response with diffuse immune hypothyroidism.
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F1
We present a 52-year-old woman with a previous medical history of locally advanced non-small-cell lung carcinoma (NSCLC) (Figure 1A-FDG-PET MIP: initial staging) with the PD-L1 expression level of 5%, treated by radiochemotherapy. After 2 years, she presented an adrenal relapse (Figure 1B-FDG-PET MIP: left adrenal relapse, arrow), which was treated with stereotactic radiotherapy and pembrolizumab, achieving a complete response (CR) after 15 months of treatment (20 cycles) [Figure 1C-FDG-PET MIP: complete response with diffuse immune hypothyroidism corresponding to immune-induced hypothyroidism by ICI (CTCAE 5.0 grade 2) that had been treated by supplementation].
Whole-body FDG-PET MIP: (A) appearance of subcutaneous and fascial hypermetabolism, (B) increase of subcutaneous and fascial hypermetabolism, and (C) disappearance of subcutaneous and fascial hypermetabolism, after corticotherapy.
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F2
After six cycles of treatment with pembrolizumab, a 2-deoxy-2-[18F] fluoro-D-glucose positron emission tomography-computed tomography (18F-FDG-PET/CT) evaluation showed the persistence of CR, however, revealing the appearance of subcutaneous and fascial hypermetabolism (Figure 2A) without any morphological or clinical translation except a transitory elevation of eosinophil count on biological analysis. A new evaluation by FDG-PET/CT was performed, showing no cancer progression but an increase in the number and intensity of hypermetabolic subcutaneous nodules and muscle fascia (limbs, paravertebral) lesions and the appearance of diffuse tracer uptake on the synovial walls of both knees (Figure 2B).
(A) Coronal l FDG PET-CT. (B) Axial FDG PET-CT. (C) Histologic feature of eosinophilic fasciitis.
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F3
To explore these hypermetabolic findings (Figures 3A, B coronal and axial FDG PET-CT views), a subcutaneous nodule biopsy was performed and histologic analysis revealed panniculitis with septal inflammation. This septal infiltrate was mostly composed of lymphocytes and few histiocytes; vessels were well seen, without vasculitis (Figure 3C HES x40).