Enterobius vermicularis

Comments:
The role of pinworms in causing acute appendicitis is controversial. The worms are often discovered incidentally in otherwise normal appendices. Pinworms are known to migrate widely and end up in organs such as uterus, fallopian tubes, ovaries, and mesentery causing granulomatous inflammation. The image shows cross-section of several pinworms in the appendix lumen. The lateral spines - an identifying feature of pinworms - are clearly seen in most of the worms.

Image courtesy of: Dr. Abdul Haleem, Dept. of Pathology, King Abdul Aziz Hospital, Al-Ahsa, Saudi Arabia.