Adult Langerhans cell histiocytosis of skull in a patient with synchronous papillary thyroid carcinoma and Castleman disease.

We report an extremely rare case of adult Langerhans cell histiocytosis (LCH) in a patient with papillary thyroid carcinoma (PTC) and Castleman disease (CD). A 46-year-old man visited our hospital with anaemia; systemic imaging showed an abdominal and a left thyroid mass. Biopsy confirmed CD for the abdominal mass and PTC for the thyroid mass. Two months after, he presented with headache and a right parietal lump. Brain CT and enhanced MRI revealed an osteolytic mass with enhancement in the right parietal skull. Surgical removal and biopsy confirmed the diagnosis of skull LCH. The BRAF mutation was positive on PTC and negative on CD and LCH. 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. We may consider of syndromic nature of these diseases to establish a treatment strategy.