case_images: PMC6777014_01
case_images: Colonoscopy.. About 4cm sized submucosal tumor was identified at the sigmoid colon.
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case_images: During the colonoscopy, a submucosal tumor sized about 4cm was identified at the sigmoid colon ( Figure 1) and biopsy was performed.
case_images: Abdominopelvic computerized tomography (CT).. A well-circumscribed, well-enhanced, round-shaped mass was identified at the sigmoid colon. (
  A) Coronal view. (
  B) Axial view.
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case_images: No intraabdominal metastasis was identified ( Figure 2A-2B).
case_images: Gross findings of the resected specimen.. (
  A) 4.5 x 4.0cm sized round, protruding mass was observed on the surface of the serosa. (
  B) The photo was taken from the mucosal side.
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case_images: On examining the resected specimen, about 4.5 x 4.0cm sized round mass was observed on the surface of the serosa and there was no tumor infiltration to the serosa ( Figure 3A-3B).
case_images: Cut section after fixation.. Relatively well-demarcated yellowish mass without encapsulation is shown.
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case_images: The mass was relatively well-demarcated without encapsulation ( Figure 4).
case_images: Hematoxylin and eosin (H&E) stain.. (
  A) The tumor cells are composed of spindle cells with low nuclear atypia. (
  B) Nuclear palisading growth pattern is shown. (
  C) Lymphoid cuffing surrounding tumor cells is shown.
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case_images: On hematoxylin and eosin (H&E) stain, the tumor was composed of spindle cells with low nuclear atypia, with nuclear palisading growth pattern, and lymphoid cuffing surrounding tumor cells were identified ( Figure 5A-5C).
case_images: Immunohistochemical stain.. (
  A) S-100 is diffuse, strong positive in tumor cells. (
  B) C-KIT is negative in tumor cells. (
  C) CD34 is negative in tumor cell, but normal vessel structures were stained. (
  D) SMA is negative in tumor cells, but normal smooth muscle in the proper muscle layer is stained.
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case_images: Figure 6A-6D). Finally, the diagnosis was a benign schwannoma of the sigmoid colon.