E-Mail karger@karger.com Novel Insights from Clinical Practice Acta Cytologica 2015;59:418–424 DOI: 10.1159/000440969 Cytological Diagnostic Approach in 3 Cases of Langerhans Cell Histiocytosis Presenting Primarily as a Thyroid Mass Nikita Oza   a Kintan Sanghvi   a Santosh Menon   b Vinita Pant   c Meenal Patil   d Shubhada Kane   b Departments of a  Cytopathology and b  Pathology, Tata Memorial Hospital, and c  Centre for Excellence, SRL Diagnostics, Mumbai, and d  Department of Pathology, Rajiv Gandhi Medical College and Chhatrapati Shivaji Maharaj Hospital, Thane, India admixture of mature lymphocytes, eosinophils and plasma cells. LCH commonly occurs in the paediatric population and young adults with the involvement of bone, skin and lymph nodes. LCH has a protracted clinical course with an overall mortality rate of 3%. Primary involvement of the thyroid gland in LCH at presentation is a rare phenomenon that can result in misdiagnosis with consequent mismanagement. Case: Ultra- sound-guided fine-needle aspiration cytology (FNAC) of the thyroid was performed in 3 cases at a tertiary cancer centre, Key Words Langerhans cell histiocytosis · Thyroid · Birbeck granules · Ancillary techniques · Fine-needle aspiration cytology Abstract Background: Langerhans cell histiocytosis (LCH) is a monoclo- nal disease of specialised histiocytes characterised by the pro- liferation of neoplastic Langerhans cells (LCs) with a varying Received: June 8, 2015 Accepted after revision: September 4, 2015 Published online: October 24, 2015 Correspondence to: Prof. Shubhada Kane Department of Cytopathology, Tata Memorial Hospital Dr. E. Borges Road, Parel Mumbai, Maharashtra 400012 (India) E-Mail drsvkane  @  gmail.com © 2015 S. Karger AG, Basel 0001–5547/15/0595–0418$39.50/0 www.karger.com/acy Established Facts • Langerhans cell histiocytosis (LCH) is a rare disease characterised by the neoplastic monoclonal pro- liferation of Langerhans cells (LCs). • The clinical spectrum is wide and can present as a solitary lesion requiring no treatment or as a mul- tisystemic life-threatening disorder which necessitates aggressive therapy. • Thyroid mass at presentation either as a primary or systemic LCH is a rare phenomenon unlikely to be suspected by the clinician. • Hence, onus of diagnosis of LCH involving the thyroid rests on the pathologist. Novel Insights • A high index of suspicion is necessary to recognise LCs in thyroid fine-needle aspiration cytology (FNAC). • LCH can be diagnosed on FNAC based on its characteristic cytomorphological features. • Diagnosis of LCH can be confirmed by immunocytochemistry (CD1a and S100). • Upfront diagnosis of LCH on FNAC obviates the need for surgery in cases of systemic involvement. Downloaded by: Tata Memorial Hospital Library 14.139.127.162 - 5/12/2016 8:34:26 AM