Splenomegaly unresponsive to standard and salvage chemotherapy in Langerhans cell histiocytosis: a case of extramedullary hematopoiesis.

Langerhans cell histiocytosis (LCH) is a proliferative disorder of dendritic cells which has evaded efforts to clearly define pathogenesis, diagnostic criteria, and therapeutic response markers. Strides have been made at classification with the recent development of a quantified score of disease severity. Splenic involvement is an indicator of poor prognosis, with spleen size its surrogate marker in evaluation and scoring. We describe a case of pediatric LCH with progressive splenomegaly despite treatment, which when examined at splenectomy revealed no LCH involvement but extramedullary hematopoiesis. These findings thus challenge our understanding of splenomegaly as a marker of disease.