RESUMO
Adenomyosis, a non-neoplastic myometrial proliferation, is a rare pathologic condition in domestic animals, of unknown etiology. There is a lack of information about the clinical and pathological features of this disease in cats, therefore just a few reports in that species. The study describes a case of adenomyosis in a feline female. A cat, six years old, undefined breed, not spayed, had abdominal swelling history and vaginal discharge. Clinically, upon abdominal palpation, a diffuse increase suggesting a uterine change was found. The vulva had sanguine-purulent exudates. The choice was for the neutering surgical. Uterine macroscopy revealed cystic endometrial hyperplasia/pyometra in uterine horns, and the presence of a diffuse mass on uterine corpus. Fragments of the mass were sent for histopathological analysis, which revealed adenomyosis of the uterine corpus. The patient exhibited adequate post-operative recovery. The adenomyosis should be considered as a differential diagnosis of uterine neoformation in domestic cats.(AU)