Risk of Second Cancer in Erdheim-Chester Disease

Erdheim-Chester disease (ECD) is a clonal-inflammatory condition driven by alterations in MAPK pathway genes such as BRAF V600E.1 Clonal hematopoiesis is reported in approximately 40% of patients with ECD,2 and approximately 10% of patients develop myeloid neoplasms, mainly consisting of chronic myelomonocytic leukemia, myeloproliferative syndromes, and myelodysplastic syndromes.3,4 More recently, an association between Langerhans cell histiocytosis and hematologic or solid malignant neoplasms was reported.5 Herein, we analyze the risk of second cancers in a large cohort of patients with ECD followed up at 2 histiocytosis centers in France and Italy.