Breyer is internationally known as a clinical expert in performing complex urethral and penile reconstruction for urethra stricture and cosmetic disfigurement, male incontinence, male fistula, surgical treatment for erectile dysfunction, and transgender surgery. He is an expert in both minimally invasive and complex open reconstructive surgery. He has a high volume reconstructive practice based primarily at the UCSF- Parnassus Heights Campus and is the Director of the UCSF Genitourinary Reconstructive Society Male Genitourinary Reconstruction and Trauma Fellowship. He has served on the American Urologic Association Guideline Panel Committees for Male Incontinence and Urotrauma.