Langerhans cell histiocytosis of the thyroid complicated by papillary thyroid carcinoma

RATIONALE Langerhans cell histiocytosis (LCH) involves mainly the skin and bone and rarely the thyroid. Meanwhile, papillary thyroid carcinoma (PTC) is the most common subtype of thyroid cancer. Both LCH and PTC could make the thyroid enlarged and hypermetabolic. The coincidence of these 2 events in a patient is rare, and this paper aimed to report such case. PATIENT CONCERNS A 40-year-old man presented with polyuria and polydipsia for 5 years. The symptoms had been relieved well by drug therapy for >4 years, until the drugs could not control the symptoms anymore and an extensively enlarged thyroid gland was noticed. DIAGNOSES Thyroid ultrasound showed a nodule with microcalcification in the upper right lobe, positron emission tomography/computer tomography scan demonstrated thyroid hypermetabolism, and fine needle aspiration (FNA) revealed PTC. Right lobectomy of the thyroid and cervical lymph node biopsy verified the diagnosis "LCH of the thyroid complicated by PTC." INTERVENTIONS The ultrasound-guided FNA biopsy was performed prior to right lobectomy of the thyroid and cervical lymph node biopsy. Postoperative histopathological examination confirmed the diagnosis, after which the patient received adjuvant chemotherapy. OUTCOMES After 5 cycles of adjuvant chemotherapy, the patient had been followed up for 2 years. LCH was controlled satisfactorily and there was no significant sign of recurrence or metastasis of PTC. LESSONS LCH of the thyroid complicated by PTC is rare. Thyroid involvement should always be considered in the differential diagnosis of LCH patients. Surgery for PTC followed by chemotherapy for LCH may be the suitable treatment.