Lisa Brenes, B.A., A.R.R.T., C.R.T (R) (M)
Supervisor of Mammography

Lisa received her Bachelor's Degree in Philosophy from Auburn University before continuing on to Huntsville Hospital to study Radiography and earn her A.R.R.T. licensure. She has been part of the John Muir Health Outpatient Imaging Team since 2008 and currently serves as Supervisor of Mammography in Walnut Creek.

Shellie Campos, M.S.N., R.N., F.N.P.-B.C., A.G.N.-B.C.
Nurse Practitioner

Shellie received her Master’s Degree in Nursing and Family Nurse Practitioner Training from Vanderbilt University. She is also certified as an Advanced Genetics Nurse and a Family Nurse Practitioner. Shellie has been with the John Muir Health Cancer Institute since 2010, where her role is to provide Nurse Navigator and Nurse Practitioner services to patients in the High-Risk Cancer Program and several John Muir Health special programs. 

Sharon Chan, M.S., C.G.C., M.P.H.
Genetic Counselor

Sharon received her Master’s Degree in Genetic Counseling from California State University at Northridge.  She has been with John Muir Health Breast Health Services since 2018.

Sheila Marquez, R.N., M.S.N., C.B.C.N.
Nurse Navigator

Sheila received her Master’s Degree in Nursing from Western Govenors University. She is also certified as a Clinical Research Coordinator and Breast Care Nurse. Sheila has been with John Muir Health since 1998. She contributed ten years each as a Medical-Surgical Nurse and Clinical Research Nurse, and currently serves as the Nurse Navigator for Breast Health Services.

Lesley Martin, M.D.
Hematology/Medical Oncology

Dr. Martin completed medical school at University of California, San Francisco. Following medical school, she completed residency training in Internal Medicine at University of California at Davis, where she remained for a fellowship in Hematology/Medical Oncology.  Dr. Martin is board certified in Hematology and Medical Oncology by the American Board of Internal Medicine. She specializes in diagnosis and treatment of blood diseases and disorders related to cancer treatment.

Bernadette Tawasha, M.A.
Office Assistant

Bernadette is the Office Assistant for the John Muir Health Breast Health Center. Her role is to register patients, collect information upon arrival, and direct patients to their specific service area (Genetic Counseling, High Risk Breast Clinic or Clinical Research). She also obtains insurance authorizations for procedures, schedules appointments and answers questions about the services we offer.

Margo Thelander, M.S., C.G.C.
Genetic Counselor

Margo received her Master's Degree in Genetic Counseling from the University of California in Berkeley, and has been with the John Muir Health Genetic Counseling Program since 2005. She previously had worked at Kaiser Permanente.

Vivian Wing, MD
Director of Medical Imaging

Dr. Wing received her Bachelor's Degree from Northwestern University, and medical degree from Northwestern University Feinberg School of Medicine. She completed her residency and fellowship at the University of California at San Diego. Dr. Wing is Board Certified in Diagnostic Radiology and has been in practice for more than 20 years.