PMC8804326_01
Case summary. (A) Clinical findings of the patient. Above: Chest computed tomography revealing a mass in the right lower lobe (arrow); below: Hematoxylin and eosin-stained tumor tissue sections presenting adenocarcinoma (magnification, x400). (B) Immunohistochemical staining showing absence of PMS2 as well as presence of MLH1, MSH2 and MSH6 in the tumor cell nuclei. (C) Capillary electrophoresis results showed loss of stability of three microsatellite biomarkers in tumor compared to the blood control, indicating high microsatellite instability. (D) Sequence chromatogram of the patient's daughter containing the same PMS2 c.1144+1G>A mutation. (E) Pedigree of the patient's family. The proband is indicated with an arrow and black denotes the cancer-affected individual.
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F1
Our proband was a 62-year-old Chinese man with 40-pack-year smoking history, presented with a consolidation shadow in the lower lobe of the right lung discovered by chest computed tomography (CT) (Figure 1A). Panscan , Genetron Health) showed a KRAS G13D mutation, a TP53 R267W mutation, and a high tumor mutational burden (TMB-H, 13.62 mutations/Mb) (Table 1). PD-L1 immunochemistry (IHC), MMR IHC, and microsatellite instability (MSI) testing revealed that his tumor was PD-L1-positive (TPS 8%), MSI-H, and dMMR (Figures 1B,C). The proband had an oncogenic KRAS G13D somatic mutation and his 38-years-old daughter with the same PMS2 variant had no cancer yet (Figure 1D). Moreover, Sanger sequencing results showed that this variant was segregated with his daughter but none of his five siblings (Figure 1E).