Final answer:
Leiomyosarcoma is the most common primary vaginal sarcoma, occurring in the smooth muscle cells of the vagina.
Step-by-step explanation:
The most common primary vaginal sarcoma is Leiomyosarcoma. It is a rare cancer that develops in the smooth muscle cells of the vagina.
Leiomyosarcoma can occur in any part of the body with smooth muscle, but it is most commonly found in the uterus and gastrointestinal tract.
One example of a primary vaginal leiomyosarcoma is a tumor that arises from the smooth muscle cells of the vagina without spreading from another site.