A multinucleate cell angiohistiocytoma (MCA) is a benign fibrohistiocytic and vascular cutaneous proliferation characterized by one or more well-circumscribed, erythematous to violaceous papules or nodules. MCAs are rare and have been reported more commonly in women in many studies, including the largest systematic literature review of MCAs, in which 79% of patients were women. The mean age of onset is 50-56 years. MCA lesions typically develop gradually over weeks to months, and most lesions are present for years before a definitive diagnosis is made.

Although the etiology is largely unknown, MCAs are thought to be reactive, with several case reports describing them arising in association with neoplasms, inflammatory processes, or trauma. Studies have also demonstrated a potential role of hormonal signaling, with increased expression of estrogen receptor alpha identified within MCAs. Some experts have also proposed that MCAs are on a spectrum of fibrohistiocytic proliferations that also includes dermatofibromas and fibrous papules, but this remains controversial.