case_images: PMC10813188_01
case_images: Immunohistochemical staining of MMR proteins. Positive expression of MLH1, MSH2, MSH6, and PMS2 in the colon tumor tissue (magnification x200) (A); MSI test electropherograms with NR-27, NR-21, NR-24, BAT25, and BAT26 markers in the colon tumor and lymph node specimens (B). MMR = mismatch repair; MSI = microsatellite instability.
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case_images: PMC10813188_01_dti-18-4_g001.jpg
case_images: fig_1
case_images: PMS2) demonstrated a homogeneous pattern of their proficiency in colon tumor tissue (Fig. 1A). Polymerase chain reaction (PCR) assay confirmed the MSS phenotype for three different colon tumor specimens (Fig. 1B). MSS phenotype in lymph node was further verified by PCR (Fig. 1B).
case_images: Chest computed tomography (CT) of the lung lesions and para-aortic lymph node lesion. Focal nodules in the lung at start of nivolumab treatment (A); 5 months after nivolumab treatment, reduction of lung nodules (B) and para-aortic lymph node lesion up to 12 mm (C); 8 months after nivolumab treatment, disappearance of lung lesions (D) and lack of growth of para-aortic lymph node lesion (E); increase of para-aortic lymph node lesion 40 months after nivolumab treatment (F).
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case_images: PMC10813188_01_dti-18-4_g002.jpg
case_images: fig_2
case_images: Approximately 2 months later, CT scans showed an increase of nodule size in the lung (Fig. 2A). In May 2019, chest CT scans confirmed the reduction of lung nodules (Fig. 2B). However, a para-aortic lymph node (PALN) on the left up to 15x12 mm was found (Fig. 2C). August 2019 (Fig. 2E). An immune stable disease (iSD) per iRECIST was recorded until September 2021, when we had to discontinue treatment due to the patient being infected with COVID-19. The administration of nivolumab was resumed; however, in April 2022, CT scans revealed an increase in the size of PALN by 7 mm compared with the baseline (Fig. 2F).