Nodular fasciitis

Nodular fasciitis (NF) is a benign, soft tissue tumor composed of myofibroblasts that typically occurs in subcutaneous tissue, fascia, and/or muscles. The literature sometimes titles rare NF variants according to their tissue locations. The most frequently used and important of these are cranial fasciitis and intravascular fasciitis. In 2020, the World Health Organization classified nodular fasciitis as in the category of benign fibroblastic/myofibroblastic tumors. NF is the most common of the benign fibroblastic proliferative tumors of soft tissue.

Nodular fasciitis is a rapidly growing, usually self-limiting neoplasm that occurs primarily but not exclusively in adults. Due to its rapid growth, NF is often misdiagnosed as a malignant tumor, usually a sarcoma. Indeed, NF was originally termed subcutaneous pseudosarcomatous fibromatosis when first described in 1955 by Konwaler et al. The correct diagnosis of a tumor as NF is pivotal to prevent its overtreatment as a more aggressive or malignant growth.

While nodular fasciitis may be precipitated by localized injuries, recent studies indicate that NFs are true neoplasms (i.e. abnormal proliferations of cells without any precipitating event). Up to 92% of NF cases have a specific type of fusion gene in their tumor cells which may be responsible for disrupting the regulation of cell growth and death.