Thirteen uterine
tumors were diagnosed in 13 cats and accounted for 0.29% of all feline
neoplasms received during a 9.6-year period. Age at diagnosis ranged from 3 to 16 years; median 9 years. Six were Domestic Shorthair cats, and 7 were purebred cats of 5 different breeds. Eight
adenocarcinomas and 1 mixed Müllerian
tumor (
adenosarcoma) comprised the endometrial
tumors. Myometrial
tumors included 3
leiomyomas and 1
leiomyosarcoma. One of the
adenocarcinomas developed in the uterine stump of an ovariohysterectomized cat; the other cats were sexually intact. Concurrent mammary
adenocarcinoma was diagnosed in 1 cat with uterine
adenocarcinoma and in another with uterine
leiomyoma.
Tumors were discovered during elective ovariohysterectomy in 2 cats, but at least 3 others had experienced reproductive problems (
infertility or
pyometra). Five cats presented for abdominal or pelvic masses. Endometrial
adenocarcinomas were positive immunohistochemically for cytokeratins and negative for smooth muscle actin (SMA): 1 of 6 cats was positive for
vimentin and 4 of 8 were positive for
estrogen receptor-alpha (ER alpha).
Adenosarcoma stromal cells were positive for
vimentin and ER alpha but negative for cytokeratins and SMA.
Smooth muscle tumors were positive for
vimentin and SMA and negative for cytokeratins.
Leiomyomas, but not the
leiomyosarcomas, were positive for ER alpha.
Adenocarcinomas in 4 cats had metastasized by the time of ovariohysterectomy. Two other cats were euthanized 5 months after ovariohysterectomy; at least one of these cats had developed an abdominal mass that was not examined histologically. Only 2 cats with endometrial
adenocarcinoma had disease-free intervals longer than 5 months after surgery.
Metastasis was not detected in any mesenchymal
tumor; however, these cats were either euthanized on discovery of the
tumor or the
tumor was first detected at necropsy.