title: Fine-needle aspiration of primary Langerhans cell histiocytosis of the thyroid gland, a potential mimic of papillary thyroid carcinoma.
abstract: The clinical presentation of Langerhans cell histiocytosis (LCH) as a primary solitary nodule in the thyroid gland is rare. As a result, there are few reports of its cytologic features in thyroid aspirates where it can pose a diagnostic pitfall. CASE AND CONCLUSION: To foster familiarity with its cytomorphology, we report the fine-needle aspiration biopsy (FNAB) findings of 3 specimens from 2 patients with LCH presenting as a solitary thyroid nodule. All aspirates contained numerous dispersed cells with prominent nuclear grooves, and the background showed a mixed pattern of chronic inflammation including scattered eosinophils. The aspirate from patient 1 raised a differential diagnosis that included chronic lymphocytic thyroiditis and a thyroglossal duct cyst, while the aspirate from patient 2 was interpreted as 'suspicious for papillary thyroid carcinoma'. The diagnosis of LCH was confirmed in both patients after lobectomy and immunohistochemical studies that revealed positive reactivity for CD1a and S-100. LCH of the thyroid gland is rare and can pose significant diagnostic challenges, but increased familiarity with its characteristic cytomorphology can help in avoiding diagnostic pitfalls.
authors.affiliation: Department of Pathology, Geneva University Hospital, Geneva, Switzerland.
authors.forename: Marc P
authors.initials: MP
authors.lastname: Pusztaszeri
authors.forename: Kenan J
authors.initials: KJ
authors.lastname: Sauder
authors.forename: Edmund S
authors.initials: ES
authors.lastname: Cibas
authors.forename: William C
authors.initials: WC
authors.lastname: Faquin
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D044963:Biopsy, Fine-Needle; D002277:Carcinoma / Q000175:diagnosis* / Q000378:metabolism; D002291:Carcinoma, Papillary; D003937:Diagnosis, Differential; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000175:diagnosis* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor