The Langerhans' cell histiocytoses (LCH) are a group of related entities which share a common pathology. The Langerhans' cell histiocytoses include eosinophilic granuloma, Hand-Schuller-Christian disease and Letterer-Siwe disease. These entities are all characterized by a proliferation of Langerhans' cells and are best thought of as mono-ostotic, polyostotic or disseminated forms of the same disease. The malignant potential of this group of diseases is uncertain and treatment should be discussed with a medical oncology member of the Lymphoma Tumour Group at one of the BCCA Centers.
True malignant histiocytosis is a rare disease and is best considered a variant form of malignant lymphoma. Hemophagocytosis by cytologically malignant-appearing cells is typically seen in histologic sections and diagnosis requires careful morphologic and phenotypic assessment. The behaviour is usually similar to that of a large cell lymphoma and treatment should be given as for large cell lymphoma taking into account the stage of the disease and the age of the patient.