Abstract
Langerhans cell histiocytosis is a clinico-pathological entity with a wide spectrum of clinical and morphological findings. The disease was defined on the basis of recognition of three entities in medical history - Hand-Schüller-Christian disease, Letterer-Siwe disease and eosinophilic granuloma of bone.
Later on in the past, these diseases were linked under a term histiocytosis X. With identification of a common cell of origin, the Langerhans cell, a name "Langerhans cell histiocytosis" (LCH) has been accepted.
This review summarizes more than a hundred-year evolution of views on the disease. Langerhans cells are identified with the aid of histopathological investigations and an ultrastructural demonstration of specific membranous intracytoplasmic structures - Birbeck granules.
At present the diagnosis of LCH utilizes immunohistochemical investigations to demonstrate positivity of S-100 protein, CD1a and langerin (CD207) in Langerhans cells. Characteristics of these molecules are briefly summarized.
Further supportive laboratory methods may be used to demonstrate expression of proteins of the cell cycle, namely Ki-67. The evaluation of the proliferation activity might support the estimation of a potential of the disease to progress or disseminate, especially in cases diagnosed at early stages or in situations they involve a single organ or tissue, and the progression might evolve secondarily.
The histopathological differential diagnosis should separate LCH from reactive non-neoplastic Langerhans cell proliferations, histocytic diseases and a number of neoplastic diseases which are briefly reviewed.