case_images: PMC9194509_01
case_images: Timeline of the patient: Chest and Abdominal contrast-enhanced CT (A-F, G1, G2, H1, H2, I1, I2); yellow circle: right lung tumor; blue circle: left pleural effusion; red circle: peritoneal effusion.
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case_images: In April 2020, computed tomography (CT) scans revealed right atelectasis, lung neoplasms, and pleural effusion ( Figure 1A ). Unfortunately, she experienced slow progressive disease (PD) with increasing lung neoplasms and emerging left pleural effusion in December 2020 ( Figures 1B-D ). However, PD was confirmed by CT showing peritoneal metastases in March 2021 ( Figures 1E, F ). A timeline illustrating the patient's medical history and therapy is presented in  Figure 1 . During the treatment, the patient's chest symptoms were relieved, and simultaneously, CA125 and CYFRA21-1 showed a decreasing trend, especially CA125 ( Figure 3 ); however, the peritoneal effusion with a chylous appearance continued to increase ( Figure 1G2 ), requiring drainage of 1000-1500 ml per day. As shown in  Figure 1 , EGFR E746_L747delinsIP (4.2%) and S1190F (0.88%) were found again without other mutations, indicating that the LUAD metastasized to the peritoneum. The ascites gradually diminished, and only a small amount of ascites was observed within the 1.5 months before the final test ( Figures 1H1, H2 ).
case_images: Next-generation sequencing (NGS) panel result showed an epidermal growth factor receptor (EGFR) mutation E746_L747delinsIP via simultaneous deletion and insertion of DNA fragments of 2 bp in exon 19.
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case_images: Repetitive NGS analysis using pleural effusion detected EGFR E746_L747delinsIP (13.7%) in exon 19 and S1190F (2.95%) in exon 28 with increasing variant allele frequencies (VAF) as per a small, customized panel covering 74 cancer target related genes in Yucebio Technology ( Figure 2 ). The ascites gradually diminished, and only a small amount of ascites was observed within the 1.5 months before the final test ( Figures 1H1, H2 ).
case_images: Serum tumor biomarkers during treatment.
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case_images: During the treatment, the patient's chest symptoms were relieved, and simultaneously, CA125 and CYFRA21-1 showed a decreasing trend, especially CA125 ( Figure 3 ); however, the peritoneal effusion with a chylous appearance continued to increase ( Figure 1G2 ), requiring drainage of 1000-1500 ml per day. Serum tumor biomarkers showed a downward trend, especially CA125, decreasing to the average level for the first time ( Figure 3 ). I2 ). Furthermore, the serum tumor biomarkers CEA and CYFRA21-1 showed an increase ( Figure 3 ). In accordance with the patient's and her family's wishes, we performed a gene test using NGS again to explore if the patient developed drug-resistant mutations.