Case for diagnosis. Solitary violaceous nodule on the toe

Reticulohistiocytomas represent a group of benign histiocytic dermal proliferations, which occur either sporadically as solitary cutaneous nodules or, when multiple, in association with systemic disease. Due to its nonspecific clinical presentation, reticulohistiocytoma may mimic other benign or malignant skin neoplasms; therefore, in most cases, a biopsy is needed in order to establish the correct diagnosis. The histology is typically characterized by the presence of large histiocytes with abundant eosinophilic cytoplasm with immunohistochemical profile positive for CD68, CD163, and vimentin. The authors report the case of a patient with solitary reticulohistiocytoma with illustrative clinical, dermoscopic, and histologic features.