Laparoscopic surgery was performed on a 16 year-old female rhesus monk
ey presenting with chronic lethargy and inappetence. The procedure rev
ealed a ''napkin-ring'' stricture located in the ascending large colon
. Histologic evaluation of the colonic lesion exhibited large numbers
of irregular acini lined by a single layer of well-differentiated neop
lastic epithelial cells. Based on the gross and histopathologic findin
gs a diagnosis of adenocarcinoma of the proximal colon was made.