The Other Histiocytosis

Excerpt

Histiocytic disorders are currently identified (“classified” is too loaded a term) by their component cells. Taking Langerhans cell disease as the prototype, we have become quite adept at identifying Langerhans cell histiocytosis (LCH) cells in tissue, and in the right clinical context, lesional cells that are CD1a+/Langerin+/S100+ can be identified with confidence, even without looking for the ultrastructural Birbeck granule. This is pretty much where the good news ends. We are as yet unable to look at individual LCH lesions in young children and pick out those that will remain confined and regress, and those that will disseminate and lead to morbidity and even mortality. There has been some suggestion that lesions containing more mature LCH cells are more likely to regress than those with immature ones [1], or that the loss of E-cadherin may be of worse prognosis [2], but these suggestions have yet to be tested prospectively. …