PMC9703460_01
Enhanced CT and follow-up CT images. White arrows indicate tumors and red arrows indicate the pulmonary artery. (A, B) Pretreatment CT scan of the patient. (C) CT scan after two doses of Tislelizumab. (D) CT scan after six doses of Tislelizumab.
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Figure 1A ) involving the pulmonary artery and without enlargement of the hilar and mediastinal lymph nodes. Furthermore, thoracic and cardiac color Doppler ultrasound revealed a small amount of pleural and pericardial effusion. Regular CT scans revealed significant improvement in pulmonary artery compression and a partial response (PR;  Figures 1B, C ) after 20 days. Tislelizumab demonstrated a sustained durable PR response [51% tumor size compared with baseline pretreatment according to RECIST version 1.1 ] with no adverse events ( Figure 1D ). The treatment timeline and therapeutic response are shown in  Figure 3 .
Pathological features of SMARCA4-UT. (A) Stained with hematoxylin and eosin. Immunostaining was negative for SMARCA4 (B), and partly or focally positive for SMARCA2 (C), CK8/18 (D), CKpan (E), SOX (F), and Syn (G). Programmed cell death ligand 1 (PD-L1) staining (H). Magnification, 100x.
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The following clinicopathological examination revealed sheets of homogenous large tumor cells with a moderate amount of eosinophilic cytoplasm, eccentrically positioned vesicular nuclei, and prominent nucleoli ( Figure 2A ). On immunohistochemistry, the mass was completely SMARCA4-negative and partly positive for SMARCA2 ( Figures 2B, C ). These tumor cells were focally positive for cytokeratin (CK), CK7, CKpan, CK8/18, and Syn ( Figures 2D-G ) and diffusely positive for vimentin. The tumor exhibited microsatellite stability (MSS), tumor mutational burden (TMB) of 23.93 muts/Mb, and high PD-L1 expression (tumor proportion score more than 90%) ( Figure 2H ) with concurrent mutations in KEAP1, TP53, and TERT.
Treatment timeline and therapeutic response.
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Tislelizumab demonstrated a sustained durable PR response [51% tumor size compared with baseline pretreatment according to RECIST version 1.1 ] with no adverse events ( Figure 1D ). The treatment timeline and therapeutic response are shown in  Figure 3 .