Abstract: A case of indeterminate cell histiocytosis was reported and related literature was reviewed. A 75-year-old female patient presented with papules and nodules for 50 days. Histopathological examination showed the epidermis was atrophic and flat, a patchy or focal histocytes and lymphocytes infiltration in the epidermis with a few foam cells and multinucleated giant cells in the middle and upper dermis. Immunohistochemistry revealed that the infiltrated cells were positive for CD43 and CD68 (histiocytoid cells), CD1a (most cells), S100 (some cells), CD163 (some cells), the Ki67 index was 30% and all cells were negative for Langerin. The diagnosis of indetermined cell histiocytosis was made. The patient took Chinese herbs herself and the lesions were slightly improved after 8 months follow-up.

Key words: histiocytosis, indeterminate cell