... The disease is a hormone related lesion, characterized by high levels of endogenous progesterone that induces exaggerated mammary glandular tissue proliferation (HAYDEN, et al., Voorwald et al. 1989), before puberty, a few weeks after estrus, during pregnancy or pseudopregnancy, or due to exogenous synthetic progestins, such as megestrol acetate (MA) and acetate medroxyprogesterone (MPA) injections, commercially available as a depot contraceptive drug for entire female cats (GÖRLINGER et al., 2002;GRIFFIN, 2001;GUDERMUTH et al., 1997;HAYDEN et al., 1981;HAYDEN, et al., 1989;JELINEK et al., 2007;NOAKES et al., 2018). In male cats, MFEH has been described after MPA or MA injection, considering that these drugs are widely used for a variety of reproductive, behavioral, and dermatologic conditions, or after accidental contact with progestin components in the environment (DORN, et al, 1983;GÖRLINGER et al., 2002;HAYDEN, et al., 1989;JELINEK et al., 2007;LEIDINGER et al., 2011;MACDOUGALL, 2003;MAYAYO, et al., 2018;MEISL, et al., 2003;PAYAN-CARREIRA, 2013;SONTAS et al., 2008). ...