Langerhans cell histiocytes with indistinct pale pink cytoplasm are illustrated here. The nuclei are often folded or notched. Letterer-Siwe disease, Hand-Schuller-Christian disease, and eosinophilic granulomas are considered to be the same basic disorder, Langerhans cell histiocytosis, with differing expressions. The Langerhans cells are monoclonal indicating that this disorder is probably neoplastic.
This disorder can lead to endstage honeycomb lung as in this case of a child with disseminated Langerhans cell histiocytosis.
Illustrated here is a characteristic EM finding in Langerhans cells; the Birbeck granule. Note the rod-like, tubular structures with a central linear density. Sometimes the terminal end is dilated giving the appearance of a tennis racket.
These non-neoplastic tumors may be confined to the lung or be part of a systemic disease such as histiocytosis X or Letterer-Siwe disease. There is an extensive histiocytic infiltrate and a xanthomatous (Gk. xanthos – yellow) appearance. Often there are other inflammatory cells including lymphocytes, plasma cells, and, as in this case, eosinophils. Giant cells may be present (not illustrated).
Eosinophilic granuloma of the lung is one of the forms of Langerhans cell histiocytosis - LCH which is often a multisystem disease. Langerhans cells are dendritic cells which are normally dispersed in various organs including the lung. Immunohistochemically they are S-100 positive and Birbeck granules can be demonstrated on EM. The list of organs which can be involved in LCH includes the hypothalamus, liver, bone, spleen, and bone marrow in addition to the lung. There is an association with smoking and an increased incidence of lung carcinoma. The lesions are bronchocentric and usually form small cysts; regression often follows cessation of smoking. Treatment modalities include cessation of smoking, steroids, cytotoxic agents, and surgery. In some cases, transplantation is required but recurrence after transplantation can occur.
From the slide collection of the late Dr. Charles Kuhn