Acute appendicitis is one of the commonest abdominal surgical diseases, the etiology of which is only fairly well established. As shown in the experimental work of Wangensteen and Bowers,13 the two important etiologic factors are obstruction and infection, and the finding of acute appendicitis without both factors is rare. Boyd2 has stated that while concretions or fecaliths are the cause of the obstruction in about 80% of the cases, other causes may also be found. Among the commoner causes are obstruction due to lymphoid hyperplasia, fibrous bands, and masses of intraluminal parasites, primarily Oxyuris vermicularis.
The occasional finding of tumor as the cause of obstruction has been reported.* Among the most important of these are carcinoids or argentaffinomas. Lee and Blain report an incidence of about 0.2% in unselected cases. Primary carcinoma of the appendix, in rare instances, may be the cause of the obstruction leading to acute