title: Secondary or second primary malignancy in the thyroid? metastatic tumors suggested clinically: a differential diagnostic task.
abstract: OBJECTIVE
  To describe the algorithms employed to explore the suggestion or consideration of metastatic malignancy in the thyroid.
  
  
  METHODS
  Thirty-seven cases with a history of malignancy (n = 21) and/or uncommon fine-needle aspiration biopsy (FNAB) findings (n = 37) were reviewed and reclassified according to The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC).
  
  
  RESULTS
  The group was heterogeneous in terms of the final histopathology results: the suggested metastasis was confirmed in only half of the cases (11/21; 52.4%). Primary thyroid malignancies were mostly nondifferentiated, medullary, or rare. However, 3 papillary carcinomas (the less common variants) were also found. Finally, 5 out of 37 cases were surprisingly benign upon histopathological investigation (uncommon repair and fibrotizing Hashimoto thyroiditis).
  
  
  CONCLUSIONS
  The metastatic nature of thyroid gland nodule(s) must be considered in cases of generalization of malignancy and/or uncommon FNAB findings. We must be as open-minded as possible from the outset. Additional techniques are helpful if available - cytoblock and immunocytochemistry can contribute substantially. Morphological comparisons with the previous malignancy are recommended whenever possible. To avoid overtreatment, cases without precise typing should not be classified as TBSRTC diagnostic category VI - malignant, but should remain in TBSRTC diagnostic category V - suspicious for malignancy. Repeated FNAB to enable additional techniques may be suggested.
authors.affiliation: Cytopathology Laboratory, Institute of Pathology, 1st Medical Faculty, Charles University and Medical College, Prague, Czech Republic.
authors.forename: Jaroslava
authors.initials: J
authors.lastname: Dušková
authors.forename: Pavel
authors.initials: P
authors.lastname: Rosa
authors.forename: Pavel
authors.initials: P
authors.lastname: Přeučil
authors.forename: Eva
authors.initials: E
authors.lastname: Svobodová
authors.forename: Jindřich
authors.initials: J
authors.lastname: Lukáš
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D044963:Biopsy, Fine-Needle; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000175:diagnosis*; D013964:Thyroid Neoplasms / Q000175:diagnosis*