myofibroma (MONDO_0006312) is a benign, localized, nodular and well-circumscribed neoplasm usually seen as a congenital neoplasm or in the first year of life. It is characterized by a biphasic growth pattern and is composed of small, undifferentiated mesenchymal cells associated with branching thin-walled vessels and more mature neoplastic spindle cells with abundant eosinophilic cytoplasm in a collagenous stroma. Also known as: lipoleiomyoma, myofibroma (morphologic abnormality).