Are fibroids a precursor to cancer?

No. Fibroids or benign tumors of the smooth muscle in the uterus, only very rarely turn malignant.
Fibroids and CA. Think of fibroids as bulging muscle in the wall of the womb. Most cancers of the uterus arise from the lining and are not related to the muscle. Cancers that start in muscle anywhere in the body are fairly uncommon. Having fibroids does not necessarily lead to cancer of the uterus.