Multinucleate cell angiohistiocytoma
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.
D23.9 – Other benign neoplasm of skin, unspecified
21985009 – Fibrohistiocytic proliferation of the skin
Differential Diagnosis & Pitfalls
- – Usually occur on the face and are often associated with tuberous sclerosis.
- – Usually occur on the leg and dimple centrally with lateral compression (Fitzpatrick sign).
- – Usually occurs on the extremities; often forms annular lesions without scale or other epidermal changes. When broadly disseminated, granuloma annulare may be associated with diabetes, while MCAs are not.
- Kaposi sarcoma (KS; and ) – Classic KS typically forms on the legs of elderly men, and epidemic KS is associated with HIV infection. KS is caused by infection with human herpesvirus type 8 (HHV-8). It usually appears more purple.
- – Most common in African Americans from the southern United States. It may be associated with pulmonary or other systemic involvement, whereas MCAs are not.
- – Groups of skin-colored to pink, small papules caused by human papillomavirus (HPV) that are most common in children. Unlike MCAs, flat warts may develop quickly and often spontaneously regress.
- – Look for grayish-white streaks (Wickham striae) overlying flat, purple papules.
- – Dark blue to violaceous papules representing dilated venules; most common on the lip or ear in older patients.