Answer: Enterobius vermicularis ovum (egg) surrounded by inflammatory cells. Thank you for all of the comments on this case!
All of you realized that this is a pinworm egg, due to the presence of characteristic features, including medium size (50-60 microns in length) and flattening on one side. The flattened side gives the egg somewhat of a "D" shape as is shown below. The eggs are fully infectious within 4-6 hours after being laid, without the need for a soil incubation phase. Therefore, infection passes easily from person to person.
Pinworm eggs are typically deposited by the female on the perianal folds of the host; however, the worms and their eggs can occasionally get lodged in folds of intestinal mucosa, or other inopportune places in the intestine (eg. diverticula, appendix) and result in formation of an abscess (as seen here).