Abstract / Summary
Abstract Background Langerhans cell histiocytosis (LCH) is a rare clonal proliferative disorder of dendrictic cell characterized by variable clinical manifestions and multisystem involvement. Thyroid involvement is exceptionally uncommon and may clinically mimic primary thyroid malignancy, creating significant diagnostic challenges. Case presentation We report a rare case of 35-year-old woman presenting with a progressively enlarging thyroid mass associated with dysphagia and hoarseness. Her medical history was notable for diabetes insipidus. Ultrasonography (USG) revealed diffuse enlargement of the thyroid gland with a dominant solid nodule in the left lobe. Fine-needle aspiration biopsy (FNAB) suggested a malignant lesion suspicious for lymphoma. The patient subsequently underwent total thyroidectomy for definitive diagnosis and treatment. Histopathological examination demonstrated diffuse infiltration of the thyroid parenchyma by atypical histiocytic cells with characteristic grooved nuclei admixed with numerous eosinophils and lymphocytes. Immunohistochemical analysis revealed strong positivity for CD1a and S100 protein, confirming the diagnosis of Langerhans cell histiocytosis. Further systemic evaluation showed no evidence of extra cervical involvement, establishing the diagnosis of isolated thyroid LCH. She was subsequently received adjuvant chemotherapy with cyratabine, along with levothyroxine and remained clinically stable for 6 – month follow-up period. Conclusions Primary thyroid LCH is an exceedingly rare entity that can closely resemble thyroid malignancy both clinically and cytologically. Accurate diagnosis relies heavily on histopathological evaluation and immunohistochemical confirmation. Awareness of this rare diagnostic possibility is important to avoid misdiagnosis and to guide appropriate systemic assessment and management.