Primary cutaneous Langerhans cell histiocytosis in an adult.

A 76-year-old man with Langerhans cell histiocytosis was admitted with an asymptomatic, dark red nodule on his left buttock. Histologic examination of the nodule showed a dense dermal infiltrate of histiocytic cells with bean-shaped nuclei; these cells reacted with antibodies to S-100 and CD1a. Ultrastructural analysis showed Birbeck granules in the cytoplasm of the histiocytic cells. Inguinal lymph node involvement subsequently developed in the patient and cutaneous nodules recurred three times in the inguinal area. Four years have passed since he first was admitted to our hospital with the cutaneous nodule on his buttock, and he is doing well without any intensive treatment except wide excision of the nodules and inguinal lymph nodes. We believe this case should be classified as one of "benign" primary cutaneous Langerhans cell histiocytosis based on the clinical course.