The attack happened in the area of 400 Greenfield Avenue between 8:30 and 8:45 p.m.
The woman said the masked man pulled her to the ground and demanded money, then cut her with a knife and fled, according to police.
The woman suffered minor injuries and went to Kaiser Permanente in Terra Linda where she was treated and interviewed by police.
The suspect is described as a white male, approximately 6 feet tall. Anyone with information on the crime is asked to call San Anselmo police at (415) 258-4665.
