We report the case of a 49-year-old woman suffering from a malignant neoplasm of Langerhans cells (LC), documented by immunohistochemical and ultrastructural analysis, and review the literature to examine and characterize the clinical and laboratory features, therapy, and prognosis of malignant neoplasms of LC. Langerhans cell histiocytosis is now regarded as a disorder of immune regulation or an inflammatory process, rather than as a malignant neoplasm. Although LC share certain features in common with ordinary histiocytes or interdigitating dendritic cells, they also differ significantly from these cells in other respects. Therefore, we propose designating a malignant neoplasm of LC 'malignant Langerhans cell tumour' and that it should be considered as a separate entity from Langerhans cell histiocytosis or other malignant histiocytoses.