REPORT OF A CASE
A 45-year-old man presented to the dermatology clinic with a solitary papule on the right forearm that had been present for approximately 9 months. The lesion was asymptomatic and had undergone no recent change in size or appearance. The patient's general health was good, with no history of arthritis. He was receiving no medications.Physical examination revealed a 7 × 8-mm, firm, red-brown, dome-shaped papule on the volar aspect of the right forearm (Fig 1). The lesion was completely excised and histopathologic examination showed a diffuse dermal infiltrate that was circumscribed and nonencapsulated (Fig 2). Within the infiltrate were numerous large, often multinucleated cells with abundant eosinophilic cytoplasm (Fig 3).What is your diagnosis?
The reticulohistiocytoses have been divided into three clinical patterns: (1) solitary cutaneous reticulohistiocytoma; (2) multiple cutaneous reticulohistiocytomas (reticulohistiocytic granuloma); and (3) multicentric
Cobb MW, Barber FA. Solitary Papule on the Forearm. Arch Dermatol. 1990;126(5):670a-670b. doi:10.1001/archderm.1990.01670290115023