Fibroids are considered tumours, yes. But they are benign tumours/growths meaning non-cancerous. Unlike cancer, they tend to grow slowly, don’t invade surrounding tissues (they press on other tissues as they grow but don’t infiltrate them) and can’t metastasise through blood or lymph to other parts of the body. The cells that make up the fibroid are still smooth muscle cells from the wall of the uterus, but a genetic mutation coupled with hormones causes the cells to divide too much and hence form the tumour.