A tumor is an abnormal growth of tissue that may be benign or malignant. Uterine fibroid tumors are benign.
From WebMD – Fibroids:
The correct medical term for what we’ve come to know as a fibroid is leiomyoma uteri. Leiomyoma uteri is a benign tumor made of smooth uterine muscle. Leio means “smooth,” my means “muscle,” and oma means “benign growth.” Fibroid tumors are therefore a collection of innocent uterine muscle cells that form a noticeable hard lump.
Wikipedia has a picture of a leiomyoma (fibroid) for those who want to take a quick look. More images can be found under Related Posts at the end.
From the Mayo Clinic – Uterine Fibroids:
Uterine fibroids are among the most common tumors in women. These noncancerous growths of the uterus may appear during your childbearing years. Also called fibromyomas, leiomyomas or myomas, uterine fibroids aren’t associated with an increased risk of uterine cancer and almost never develop into cancer.
From the National Institutes of Health’s publication “Fast Facts about Uterine Fibroids“:
Uterine fibroids are not cancerous. Fibroids are not associated with cancer; they rarely develop into cancer (in less than 0.1 percent of cases).
If you are still concerned about your risk of cancer in association with uterine fibroid tumors, talk to a health care professional.