case_images: PMC9880525_01
case_images: Flow of diagnosis and treatment. CT, computed tomography; SD, stable disease; XELOX, Capecitabine + Oxaliplatin regimen.
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case_images: She had a change in stool pattern and habit for 8 months and anal pain with bloody stools for 6 months ( Figure 1 ). Multiple lymph node shadowing on the left side of the abdominal aorta, left parietal iliac vessels, right iliac fossa, and pelvic mesentery with partially increased metabolic activity was considered as metastasis (Supplementary Figure 1).
case_images: CT scans showed the chronological response of the patient following a series of treatment. The red arrow represents the area of the target lesion.
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case_images: The lesion broke through the serosa, with the surrounding fat gap blurred and the peritoneum, omentum, multiple irregular soft tissue nodules around the superior rectal artery, and presacral fascia multiple nodular enhanced; thus, the possibility of metastasis was considered ( Figure 2 ). The carcinoembryonic antigen (CEA) was 23 and carbohydrate antigen 19-9 (CA19-9) was 337.1 (Supplementary Figure 2).
case_images: Coloscopy revealed the shrinking of the tumor following a series of treatments.
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case_images: f3
case_images: The colonoscopy suggested a new invasion of the intestine 5-13 cm from the anal verge, with localized erosion and necrosis ( Figure 3 ). Then, on account of genetic testing that revealed KRAS WT, NRAS WT, BRAF V600E mutation, MSS, and high tumor mutation burden (TMB) (9.75 mutations/Mb) (Supplementary Figure 3), the chemotherapy regimen was changed to XELOX + Bevacizumab for four cycles, and radiotherapy (CTV 50Gy/25F, PTV 50Gy/25F) was administered simultaneously from February 2021 to May 2021.
case_images: HE and IHC staining on tumor tissues of the patient after chemotherapy, immunotherapy, and surgery: (A) HE staining; (B) IHC staining of CD3; (C) IHC staining of PD-1; (D) IHC staining of CD8. (A, C), at 100x magnification; (B, D), at 200x magnification).
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case_images: The postoperative pathological biopsy found no signs of malignancy and only suggested chronic inflammation of the mucosa with focal lymphoid tissue reactive hyperplasia ( Figure 4A ). Meanwhile, immunohistochemistry (IHC) revealed tiny amounts of CD3 (+) ( Figure 4B ), scattered CD8 (+) ( Figure 4D ), and minor amounts of PD-1 (+) ( Figure 4C ).