Figure 3.

Section of a rectal carcinoid tumor obtained by endoscopic mucosal resection. A: Low-power photomicrographs demonstrating a carcinoid tumor, which is present in both the mucosa and submucosa of the rectum, with tumor-free surgical margins (HE, original magnification x 4); B and C: tumor cells arranged in nests and rosette-like structures, with absence of nuclear pleomorphism and mitotic figures (HE, original magnification x 200 and x 400, respectively); and D: chromogranin staining of the tumor cells demonstrating prominent chromogranin immunoreactivity (original magnification x 200).