Pathognomonic Pipet Abscess.
The location of the spherical abscess at the base of the right horn is highly suggestive of a pipet abscess. When a treatment pipet is passed through the cervix it is relatively easy to perforate the uterine wall anterior to the internal os of the cervix, especially in an infected uterus. Contamination from the lumen then directly invades the wall. The endometrium may heal over the area and create a firm localized abscess.
Drost M (1970)