PMC10040595_01
Colonoscopy showing an ulcerative mass, approximately 3 * 3 cm in size, located in the sigmoid colon 15 cm proximal to the anal verge (A). Scattered raised lesions with a size of 0.4-1.0 cm located in the colon and rectum (B).
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Colonoscopy was performed, and an ulcerative mass, approximately 3 * 3 cm in size, was seen in the sigmoid colon 15 cm proximal to the anal verge ( Figure 1A ), which was diagnosed as colon cancer. In addition, scattered lesions with a size of 0.4-1.0 cm could be seen in the colon and rectum ( Figure 1B ).
Adenocarcinoma and neuroendocrine tumor (NET) were noted in separate areas, but some areas showed cross-growth.
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The two coexisting, distinct tumor types were noted in separate areas, but other areas showed cross-growth ( Figure 2 ).
Immunohistochemical analysis revealed that the neuroendocrine component was positive for CD56, Syn, and CgA, and Ki-67 proliferation index was <2% and thus considered neuroendocrine tumor (NET) G1.
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The other component was slightly positive for CK and Rb and was positive for CD56, Syn, and CgA ( Figure 3 ), indicating that it was a neuroendocrine component. Ki-67 proliferation index was <2% ( Figure 3 ), so it was diagnosed as NET G1.
Some lymph nodes around the resected intestinal segment were invaded by neuroendocrine tumor (NET) G1.
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NET G1 ( Figure 4 ). No tumor was found in the biopsy of the proximal anastomosis, while a NET G1 was found in the distal anastomosis.