title: Flow cytometry in the differential diagnostics of Hashimoto's thyroiditis and MALT lymphoma of the thyroid.
abstract: BACKGROUND
  A combination of traditional cytology methods with fluorescence activated cell sorting (FACS) analysis of fine-needle aspiration biopsy (FNAB) material is considered a powerful diagnostic tool in the differential diagnosis of thyroid lesions suspected of mucosa-associated lymphoid tissue lymphoma (MALT-L). The aim of this study was to demonstrate the FACS-based diagnostic process of thyroid lesions in a clinical situation where ultrasound and cytological examinations did not allow differentiation between Hashimoto's thyroiditis (HT) and MALT-L.
  
  
  METHODS
  The patients analysed in this study presented significantly different clinical courses of thyroid disease: quickly enlarging painless tumour of the thyroid right lobe in the first case, and chronic HT with palpable tumour in the thyroid isthmus in the second patient. Due to the suspicion of MALT-L resulting from indeterminate ultrasound and FNAB-cytology results, FNAB material was obtained from all the previously examined thyroid lesions and directly subjected to FACS assessment, encompassing κ/λ light chain restriction analysis, as well as measurements of B and T cell surface antigens.
  
  
  RESULTS
  The FACS analysis of FNAB material obtained from our patients did not show any definite signs of light chain restriction. Although one of the samples showed a borderline value of κ/λ ratio (κ/λ = 0.31), further immunophenotyping confirmed clonal expansion in none of the examined thyroid regions. Histopathological findings documented the diagnosis of HT in both clinical cases.
  
  
  CONCLUSIONS
  We believe that FACS represents a useful and reliable complementary diagnostic measure in FNAB-based differential diagnosis of lymphoproliferative thyroid disorders.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Adamczewski
authors.forename: Mariusz
authors.initials: M
authors.lastname: Stasiołek
authors.forename: Marek
authors.initials: M
authors.lastname: Dedecjus
authors.forename: Piotr
authors.initials: P
authors.lastname: Smolewski
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, Poland Department of Endocrinology and Metabolic Diseases, Polish Mother's Memorial Hospital - Research Institute, Lodz, Poland. alewin@csk.umed.lodz.pl.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Lewiński
mesh_terms: D044963:Biopsy, Fine-Needle; D003937:Diagnosis, Differential; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*