Mr Gui has both a private and an NHS practice at The Royal Marsden. He is a specialist breast and reconstructive surgeon. He trained in general surgery, surgical oncology and breast reconstruction surgery in the UK and USA. He is a member of the British Breast Group, the Surgical Research Society, the Association of Breast Surgery and the British Association of Surgical Oncology.
Mr Gui is on the steering committees of a number of national training courses, and is on the trial management committees of national and international studies in screening moderate- and high-risk women, the intraductal approach to breast cancer and neo-adjuvant endocrine therapy. His speciality and research interests include sentinel node biopsy, risk reduction mastectomy, duct endoscopy, and oncoplastic and breast reconstruction surgery.