Necrobiotic xanthogranuloma without periorbital involvement: an ultrastructural investigation.

A case of necrobiotic xanthogranuloma without typical periorbital involvement is described at the ultrastructural level. The patient, a 58-year-old Italian man, presented in 1995 with a brief history of nodulo-papular lesions commencing on the lower limbs, and mild paraproteinemia. During 6 years of follow-up, anemia, neutropenia with marked lymphopenia, and increased ESR were found, while serum cholesterol and triglyceride levels decreased from hyper to hypo values. Systemic diseases, such as diabetes, malignancy, or extracutaneous lesions, often associated with NXG, have not developed. Conventional histology was distinctive for NXG, and immunohistochemistry confirmed that dermal histiocytes were not of Langerhans cell lineage. At ultrastructure, regeneration and degeneration ("regen-degen") features were observed in some individual deep dermal histiocytes, which have not been previously documented in the literature. Identification of giant histiocytes showing 'regen-degen'' aspects might prove to be a useful ultrastructural diagnostic marker for NXG.