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. When the term fibroma is used without modifier, it is usually considered benign, with the term fibrosarcoma reserved for malignant tumors.

A mesenchymal neoplasm characterized by solitary or multiple nodules involving the skin, striated muscles, bones and, sometimes, viscera. It usually appears as a subcutaneous nodule, but can also appear as an ulcer, pedunculated lesion, or similar to a hemangioma. Histology shows well-circumscribed tapered cell lobes, resembling smooth muscle cells. At its center, perivascular round cells (hemangiopericitoides) are usually observed, giving a biphasic appearance.