Pelvic aneurysmal bone cyst in a dog.

A three-year-old male Siberian Husky dog was referred to the Veterinary Teaching Hospital in Osaka Prefecture University with a complaint of difficulty in expelling the stools. By rectal examination, a mass as big as a fist could be detected occupying the cavum pelvis. Radiographically the mass had a thin bony shell bulging from the pubic periosteum. In the shell, radiolucent trabeculation gave the area a "soap bubble" appearance. The cut surface of the removed mass showed a honeycomb-like pattern constituted of some small loculate bony cysts. These cysts were separated from each other by a fibrous or bony trabeculae with blood-filled vascular channels or sponge-like structures. From clinical and pathological findings, this mass was diagnosed as a pelvic aneurysmal bone cyst. After surgery, the patient completely recovered without tenesmus.