Orbital and ocular adnexal histiocytic tumors; a multidisciplinary literature review

Purpose: To review and update the clinical presentation, pathology, treatment strategies, and follow-up of the orbital and ocular adnexal histiocytic tumors. Methods: The review included the publications in English literature up to January 2024. Results: Out of 263 screened publications, 73 studies on Langerhans cell histiocytosis (LCH), juvenile and adult onset xanthogranuloma (JXG, AOXG), Erdheim-Chester disease (ECD), Rosai-Dorfman disease (RDD), and histiocytic sarcoma (HS) were included. Diagnosis is based on histological characteristics and markers on immunohistochemical staining. Treatment options vary depending on the type of histiocytic tumors, number of lesions, number of involved organs, and presence of vital organ involvement such as central nervous system. Surgery is the first diagnostic step for all and serves as the primary treatment for LCH and XG. Systemic chemotherapy is the primary treatment for EDC, RDD, and HS and the treatment of choice for the patients with multifocal or multi-organ involvement as well as recurrent or refractory lesions, regardless of the type of histiocytic tumor. Radiotherapy is an adjunctive primary treatment for the patients with HS. It is reserved for recurrent or refractory lesions in the other types. Targeted therapy is currently in progress and may replace the systemic chemotherapy in patients with LCH, XG, and EDC. Conclusion: Surgical debulking is diagnostic in all and therapeutic in LCH, JXG, and AOXG. All recurrent, refractory, multifocal, and multi-organ tumors require additional systemic chemotherapy with or without radiotherapy. Follow-up imaging every 3 to 6 months for the first 2 years and then annually is recommended.