Cornish Rex Case

Species: Feline
Breed: Cornish Rex
Age: 3 mos
Gender: Male Intact


Mammary Gland.

Click here for the IDEXX Pathology Report on this case.

Microscopic Description:

Mammary gland: The mammary gland is expanded by hyperplastic ducts surrounded by multiple layers of fibroblasts embedded within an edematous stroma that blends into dense bands of collagenous stroma. Ducts are lined by 1-3 layers of cuboidal to columnar epithelial cells. The surrounding spindle cells have indistinct cell borders, a scant amount of eosinophilic cytoplasm, an oval nucleus with stippled chromatin and small nucleoli.

Microscopic Interpretation:

Interpretation:  Mammary gland: Fibroepithelial hyperplasia

Excision:  Surgical excision is complete, therefore local recurrence is unlikely.

Vascular Invasion: Not Observed


Fibroepithelial hyperplasia is a benign nonneoplastic proliferation of mammary ducts and connective tissue of young intact cats, pregnant cats, or older neutered male and female cats on prolonged progesterone therapy. There is regression following ovariohysterectomy or termination of pregnancy or progesterone therapy. The pathogenesis is directly related to prolonged exposure to endogenous or exogenous progesterone or progesterone therapy. Clinically, there is sudden rapid uniform enlargement one or more mammary glands. These masses are firm and painless, unless ulcerated.

Image Notes:

  1. Low magnification view of the lesion (as submitted), demonstrating proliferation of glandular structures within fibromatous stroma.
  2. Higher magnification view of the lesion, demonstrating loose fibrous stroma surrounding the glandular structutres.

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