Langherhans cell histiocytosis (LCH) and Erdheim-Chester (EC) are two histiocytic disorders which occurrence in the same patient has rarely been described. Thyroid involvement of LCH is rare, and concurrent papillary thyroid carcinoma (PTC) exceptionally reported. We report a case of a 73 year old man who presented a diagnosis of mixed histiocytosis LCH and EC. The patient suffered of insipidus diabetes since 1 year without pituitary abnormality but clinical examination showed periorbital xanthelesma. Systemic involvement was confirmed with bilateral sclerotic bone lesions, retroperitoneal fibrosing disease.Bone biopsy showed infiltration of histiocytes with kidney-shaped nuclear and eosinophilic cytoplasma. Histiocytes were CD1a, protein S 100 positive and CD 68 negative and expressed mutation BRAF V600E. Treatment with vemurafenidwas started. Also this patient had two thyroid nodules (27 and 14 mm) hypoechogenic, Tirads 4 without fixation on the Pet/CT - Ultrasound-guided fine needle aspiration (FNA) of the thyroid was suspicious for malignancy (Bethesda 5). Total thyroidectomy was performed. There was no thyroid histiocytosis involvement but an incompletely capsulated papillary carcinoma with follicular pattern and capsular minimal invasion without BRAF V600E mutation. No lymph node invasion was noted.Radioactive iodine therapy (30 mci) under recombinant TSH was delivered with efficacy: 6 months later, thyroglobulin was undetectable without circulating antibody and neck ultrasound was normal. LCH can involve thyroid and cervical lymph nodes, and could coexist with other thyroid diseases such as chronic lymphocytic thyroiditis. PTC may be exceptionally associated and should be considered in the differential diagnosis. Moreover, FNA cytological diagnosis of LCH is difficult. Activating missense mutation BRAF V600E has been identified in multiple neoplasms including melanoma, colorectal carcinoma but also papillary thyroid carcinoma and histiocytosis (LCH, EC). Two cases reported LCH associated with a BRAF V600E mutation in PTC. Unfortunately this mutation was absent in our case of PTC.
18 - 21 May 2019
European Society of Endocrinology