title: The unique liquid-based cytologic findings of thyroid signet-ring follicular adenoma: a report of two cases with fine needle aspiration cytology.
abstract: BACKGROUND
  Signet-ring follicular adenoma is a rare variant of follicular neoplasm, which has only been described using the conventional smear cytologic preparation. Here we report the unique cytologic findings of two cases of signet-ring follicular adenoma using liquid-based samples and corresponding histologic features and results of ancillary tests.
  
  
  METHODS
  Case 1: A 65-year-old man presented with a solitary nodule in the right lobe of the thyroid. Ultrasound-guided fine needle aspiration (FNA) yielded several groups of microfollicles containing colloid or mucin-like globules. The tumor cells had eccentrically located nuclei compressed by distended luminal globules. Case 2: A 51-year-old woman presented with a nodule in the left lobe of the thyroid. On liquid-based cytology, cord-like arrangements of microfollicules were noted. The tumor cells had large, clear vacuoles, but the nuclei maintained their round shape and central location.
  
  
  CONCLUSIONS
  The liquid-based cytologic characteristics are quite different from those encountered in the conventional smear of FNA; therefore, pathologists must also be familiar with the cytomorphologic characteristics of liquid-based preparations. In addition, given the distinctive cytological and histological appearance and the benign clinical course, signet-ring follicular adenoma should be distinguished from other metastatic neoplasms displaying signet-ring cell features.
authors.affiliation: Department of Pathology, Chung-Ang University College of Medicine, Seoul, South Korea.
authors.forename: Yoon Yang
authors.initials: YY
authors.lastname: Jung
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Kim
authors.forename: Tae Jin
authors.initials: TJ
authors.lastname: Lee
authors.forename: Chung Hun
authors.initials: CH
authors.lastname: Lee
authors.forename: Chae Young
authors.initials: CY
authors.lastname: Lee
authors.forename: Hyebin
authors.initials: H
authors.lastname: Lee
authors.forename: Han Suk
authors.initials: HS
authors.lastname: Ryu
mesh_terms: D000236:Adenoma / Q000473:pathology*; D000368:Aged; D044963:Biopsy, Fine-Needle; D002467:Cell Nucleus / Q000473:pathology; D003581:Cytodiagnosis / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013964:Thyroid Neoplasms / Q000473:pathology*; D014617:Vacuoles / Q000473:pathology