Long-term remission of unusual plasmoacanthoma on the nasal canthus achieved by intralesional corticosteroid injection: Insights into the pathogenesis and treatment planning based on a literature review.

Plasmoacanthoma (PA) is a verrucous tumor predominantly developing on periorificial areas, which has been considered as an unusual subtype of plasmacytosis circumorificialis. Because of its rarity and clinical resemblance to several verrucous dermatological disorders, accurate diagnosis of PA is quite challenging. Herein, we present an extremely unusual case of PA which arose on both sides of the nasal canthus and was successfully treated with intralesional corticosteroid injections. To elucidate clinicopathological features of this condition, a literature review was also attempted. A 78-year-old woman visited us with a 2-year history of eruptions affecting both sides of the nasal canthus. At a local clinic, the diagnosis and treatment had been unsuccessful due to non-specific histological findings, leading to the referral to our institute. On physical examination, verrucous and lobulated reddish plaques were observed. In histology, psoriasiform epidermal change and dense plasma cell infiltration in the dermis were detected. The diagnosis of PA was made. After 5-monthly intralesional triamcinolone acetonide injections, the lesions became hardly noticeable with no evidence of recurrence. A literature review found five PA cases. PA predominantly arose on the periorificial area, mostly in or around the mouth, except one case which developed on the extra-oral or perioral area. Intralesional corticosteroid injection has been preferably performed, which frequently achieved successful remission. Chronic inflammation has been reported as a preceding condition. Abundance of plasma cells in the lacrimal glands and conjunctiva, together with pre-existing allergic conjunctivitis and habitual scratching, might have contributed to PA development in our case. Histopathological detection of psoriasiform epidermal change and dense dermal plasma cell infiltration is indispensable for the diagnosis of PA. For accurate diagnosis, optimization of treatment, and further accumulation of extra-oral/perioral PA cases, a skin biopsy needs to be proactively performed on verrucous lesions on relatively unfamiliar orifice sites.