Reticulohistiocytoma, also known as solitary epithelioid histiocytoma, is a rare but well-documented histiocytic proliferation of the skin and soft tissues. It is a non-Langerhans cell histiocytic lesion that typically affects adults. According to the revised classification of histiocytic disorders, solitary reticulohistiocytoma (SRH) is listed under the C group (xanthogranuloma family). Another form, which is also listed under the C group, is multicentric reticulohistiocytosis, in which patients present with extensive cutaneous and joints involvements.

https://www.canadianjournalofophthalmology.ca/article/S0008-4182(20)30708-0/fulltext