Fig. 2

Endoscopy images, gross pathology, and histopathology from case 2. a Colonoscopy revealed an ulcerated, partially obstructing, large mass in the transverse colon (marked by asterisk). The pediatric colonoscope could not completely traverse this large mass due to tumor obstruction and alteration in the normal colon anatomy. b Upper endoscopy showed a large malignant ulcerated mass (marked by asterisk) with no bleeding in the second part of the duodenum. c Part of the surgical specimen including colon (marked by single arrow), duodenum (marked by double arrow), with the mass (marked by asterisk) with a diffusely mucinous appearance. d Hematoxylin and eosin stain of primary colonic adenocarcinoma (viewed at ×40) with large pools of mucin evident. The tumor was 14 cm, low grade mucinous adenocarcinoma of the colon with loss of mismatch repair proteins and high microsatellite instability. There was mild to moderate intratumoral lymphocytes, mild to moderate peritumor lymphocytes, with low grade tumor budding, and no lymphovascular invasion. Margins were negative and 22 lymph nodes were negative (not shown)