We report an extremely rare case of adult Langerhans cell histiocytosis (LCH) in a patient with papillary thyroid carcinoma (PTC) and Castleman disease (CD)...The BRAF mutation was positive on PTC and negative on CD and LCH....The biopsy showed PTC, corresponding to T3N0M0 in the pathological staging system.9 B-type Raf proto-oncogene serine/threonine kinase (BRAF) V600E mutation was detected using real-time PCR....We conducted surgical resection only for PTC and LCH; surgical resection with siltuximab for multicentric CD. At the 25-month follow-up, there was no recurrence or progression.