PMC10188995_01
Multiple liver metastases limited to right liver lobe in MRI at diagnosis in September 2019 (white arrows).
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A 47-year-old man without any significant pre-existing conditions was diagnosed in September 2019 with a rectum adenocarcinoma (upper rectal) with synchronous liver metastases (limited to right liver lobe) (see the magnet resonance imaging (MRI in  Figure 1 ).
PET-CT scans: (A) November 2021; diffusion restriction at the resection margin with albeit minimal FDG activity (white arrow), (B) May 2022; clear increase of FDG activity in the resection margin in liver segment IV.
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To further classification of the contrast medium enhancement, subsequently conducted 2-Deoxy-2-[18F]fluoro-d-glucose emission tomography (FDG-PET-CT) showed diffusion restriction at the resection margin with albeit minimal FDG activity (white arrow; Standardized uptake value (SUV) max 4.3), which fell within the range of the liver parenchyma (SUV 1.9-4.8) (See PET-CT scan in  Figure 2A ). This PET-CT revealed a clear increase of FDG activity in the resection margin in liver segment IV (See PET-CT scan in  Figure 2B ).
Longitudinal liquid biopsy results: The first three liquid biopsy analyses until the 15th month of the follow up were negative. The fourth sample revealed NRAS (red)- and TP53-(circles blue) mutations. Only after the resection (arrowhead), the ctDNA was no longer detectable. Three months after the reappearance of the NRAS2 C12D mutations, the CEA level also increased substantially.
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The metastasis tissue was graded as G2 with 50% necrotic parts. No hint for microsatellite instability was found. The postoperative liquid biopsy samples no longer contained ctDNA with NRAS or TP53 mutations. The tumor marker carcinoembryonic antigene CEA was not substantially elevated until March 2022 and decreased to normal after surgery in July 2022 ( Figure 3 ).