case_images: PMC10113508_01
case_images: Imaging performance. (A-C) Enhanced CT of the chest and abdomen before treatment showed a dense mass shadow of soft tissue in the anterior mediastinum, multiple retroperitoneal lymph nodes enlarged and fused into a mass, and left liver occupancy. (D-F) After 2 months of tislelizumab combined with epirubicin treatment, the CT showed a significantly smaller lesion shadow than before, and the efficacy evaluation was PR. (G-I) In April 2022, Chest CT showed that the size of the anterior mediastinal hypodense foci was similar to that before. CT of abdominopelvic cavity showed multiple posterior peritoneal and perihepatic occupations with increased lesion extent compared to previous CT, and some of the lesions were new. Suspicious new nodules in segment VI of the liver, and efficacy evaluation of PD.
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case_images: Chest CT showed mediastinal lymphadenopathy and enhancement, a soft-tissue density mass and nodular shadow in the anterior mediastinum with a maximum diameter of 100 mm; involvement of the anterior chest wall, pericardium, and liver capsule; retroperitoneal lymphadenopathy merged into the mass; and left hepatic occupancy on August 2, 2021 ( Figure 1A ). Enhanced abdominal and pelvic CT on August 3, 2021 uncovered multiple masses in the posterior peritoneum, anterior gastric margin, perihepatic and anterior mediastinum, which were considered malignant lesions ( Figures 1B, C ). Two months later, CT was repeated, and the lesion had significantly regressed ( Figures 1D-F ). In April 2022, repeat chest CT suggested a stable disease ( Figure 1G ); however, abdominal CT uncovered multiple lesions in the posterior peritoneal, perigastric, and perihepatic occupancies with an increased range of lesions compared to the previous findings. Some lesions were new, suspicious nodules in segment VI of the liver, newer than before, and metastases to be excluded ( Figures 1H, I ).
case_images: Pathological results. (A-C) Structural destruction in lymphoid tissue, diffuse hyperplasia of heteromorphic tumor cells, large size of tumor cells, obvious pleomorphism, spindle-shaped and polygonal, large and deep stained nuclei and irregular pseudoinclusion bodies in nuclei, multinucleated and giant tumor cells in some tumor cells, multiple nucleoli, mitotic images are easy to see (magnification x 40, 20, 40). (D-H) IHC staining showed sequentially CKpan, CAM5.2, EMA, Vimentin, Ki67 (+). (I) Localized aggregation of lymphocytes to form nodules, and the formation of a central germinal center of the nodule is seen, consistent with tertiary lymphoid structures. (J) Positive for PD-L1 (Dako22C3).
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case_images: P63, CD35/CR1, CD79a, PAX-5, D2-40, and WT-1 ( Figure 2 ). Combined with the previous IHC results, the findings were consistent with a diagnosis of UPS. PD-L1 was highly expressed, and the TPS was approximately 80% (Dako22C3).
case_images: Review of treatment process. Treatment process and effect evaluation of the patient. PFS, progression-free survival; PR, partial response; SD, stable disease; PD, progressive disease.
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case_images: The primary treatment timeline is shown in  Figure 3 .