Fibroma of the ovary. Light micrograph (LM) of a fibroma of the ovary. Fibromas (or fibroid tumors or fibroids) are benign tumors that are composed of fibrous or connective tissue. They can grow in all organs, arising from mesenchyme tissue. The term "fibroblastic" or "fibromatous" is used to describe tumors of the fibrous connective tissue. Magnification: x100 when printed at 10 centimetres wide. Human tissue.