Feline Mammary Hyperplasia Study Guide

Overview and Clinical Importance

Feline mammary hyperplasia (also known as fibroepithelial hyperplasia, fibroadenomatous hyperplasia, or mammary hypertrophy) is a benign, progesterone-dependent condition characterized by rapid, non-neoplastic proliferation of mammary ductal epithelium and stroma. This condition accounts for approximately 13-20% of all feline mammary masses, making it an important differential diagnosis on the NAVLE.

Understanding this condition is critical because over 80% of feline mammary masses are malignant. Differentiating benign hyperplasia from mammary carcinoma has significant implications for treatment planning and prognosis. The condition is highly responsive to appropriate medical therapy, making accurate diagnosis essential for optimal patient outcomes.

Etiology and Pathophysiology

Hormonal Mechanism

The primary driver of feline mammary hyperplasia is progesterone, which can be either endogenous (from ovarian corpora lutea during diestrus, pregnancy, or pseudopregnancy) or exogenous (from synthetic progestins such as megestrol acetate or medroxyprogesterone acetate).