PMC9377458_01
Images of pulmonary mediastinum CT and echogatstroscopy. (A) Transverse position and (B) sagittal position of pulmonary mediastinum CT show a mass located in the right posterior mediastinum approximately 37 x 28 x 67 mm in size, and the boundary with the adjacent esophagus is unclear. (C) The white light endoscopy view and (D) endoscopic ultrasound image show a 34.5 mm x 32.6 mm semispherical uplift with smooth surface mucosa and intraluminal growth pattern originating from the esophageal submucosal layer, with uniform hypoechoic change and a clear boundary.
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Computed tomography (CT) imaging showed a soft tissue mass shadow in the right posterior mediastinum approximately 3.7 x 2.8 x 6.7 cm in size, and the boundary with the adjacent esophagus was unclear (Figures 1A, B). The boundary remained clear with uniform hypoechoic changes (Figures 1C, D).
Microscopy images of the GIST. (A) The tumor demonstrated short spindle cells with red homogeneous stroma and pale blue mucus stained by H&E (200x). (B) The tumor cells showed an unequal positive cytoplasmic signal for CD117 (200x). (C) The tumor cells showed a weakly positive cytoplasmic signal for DOG1 (200x). (D) The tumor cells showed a negative cytoplasmic signal for SMA (200x). (E) The tumor cells showed a positive cytoplasmic signal for CD34 (200x). (F) The tumor cells showed a positive cytoplasmic signal for SDHB (200x). (G) The Ki-67 labelling index was 1% (200x). (H) A break-apart fluorescent in situ hybridization (FISH) assay found FGFR2 translocation (100x).
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The histological examination revealed that the tumor consisted of short spindle cells with red homogeneous stroma and mucoid degeneration (Figure 2A) with a mitotic index of < 5/5 square mm2. On immunohistochemistry, the tumor cells were unequally positive for CD117 (Figure 2B), weakly positive for DOG1 (Figure 2C), negative for SMA (Figure 2D), strongly positive for CD34 (Figure 2E), and positive for SDHB (Figure 2F). The Ki-67 labelling index was 1% (Figure 2G). FGFR2 translocation (Figure 2H). Follow-up was suggested for this patient.
(A, B) The representative chromatogram of Sanger sequencing. (A) The forward sequencing result at exon 9 of c-KIT for the GIST in this case. (B) The reverse sequencing result at exon 9 of c-KIT for the GIST in this case. (C) NGS revealed the presence of the FGFR2-KIAA1217 gene fusion (3.88% abundance in tissue).
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Sanger sequencing revealed no mutations in the exons corresponding to the c-KIT and PDGFRA genes, including exons 9, 11, 13 and 17 of KIT and exons 12, 14 and 18 of PDGFRA (Figures 3A, B). Next-generation sequencing (NGS) revealed the presence of an FGFR2-KIAA1217 gene fusion (3.88% abundance in tissue, Figure 3C).