Samuel N. Marcus M.D., Ph.D.



Caroline Luczak, PA

Samuel Marcus, MD, PhD, FRCP(London), AGAF

Joanne Marcus, PA

Caroline Luczak graduated with her Master of Physician Assistant Sciences with Honors from Gannon University in Erie, Pennsylvania in 2019. She has been certified with The National Commission on Certification of Physician Assistants since September 2019 and the California Physician Assistant Board since October 2019.

  She began her career working autonomously at a Bay Area urgent care clinic prior to joining Dr.Marcus’ practice. She currently works as a Physician Assistant in two specialties, cardiology and gastroenterology. She joined Dr. Samuel Marcus’ gastroenterology practice in January 2021. In addition to managing patient’s acute and chronic health issues, she places a strong emphasis on health promotion and disease prevention.

Originally from Barrie, Ontario Canada, Caroline is a huge ice hockey fan. She is a former Division I ice hockey player, playing for her undergraduate university, Mercyhurst University in Erie, PA. In her spare time Caroline still enjoys playing and coaching.

Dr. Marcus is a Board Certified Gastroenterologist  who has been practicing in Mountain View, California since 1992. He is particularly interested in the early detection and prevention of colon cancer, the diagnosis and management of Crohn’s disease and ulcerative colitis and the endoscopic management of obesity.



Top Doctor in Gastroenterology in San Francisco Bay Area: 2000-2014,Castle Connolly’s America’s Top Doctors

Top Doctor in Gastroenterology: 2013, US News and World Report

Healthgrades Recognized Doctor

Top Doctor in Gastroenterology: 2000-2003 San Jose Magazine

To have the opportunity to work in the medical field has been my calling since childhood. In fact, I come from a family of physicians. In the United Kingdom I was a practicing pharmacist.


In 2006, I became a licensed physician assistant after graduating from the Physicians Assistant (PA) Program at Stanford University School of Medicine. After practicing primary care medicine, I subsequently joined my husband Dr Samuel Marcus where, under his close guidance and supervision, I help him look after his patients suffering from diseases and disorders of the gastrointestinal tract and liver. I pride myself in my ability to make patients feel comfortable about discussing with me what to some of them, can be embarrassing and distressing symptoms.


It is not unusual that patients can be quite worried when they are referred to see Dr Marcus. As a PA I am afforded the time to listen closely, discuss, advise, and under the direction of Dr Marcus, recommend the appropriate investigations to help diagnose and manage their complaints.