Due to the introduction of fine needle aspiration cytology (FNAC) to the routine clinical preoperative egamination surgical pathologists are faced with thyroid gland specimens with FNAC-induced secondary changes. These changes can cause diagnostic difficulties and be a Bource of incorrect diagnosis. Authors present a review of FNAC-induced changes with differential diagnostic criteria helpful in these pitfalls. FNAC-induced changes can be schematically divided finto two major groups - recent ones (intranodal bleeding and/or necrosis) and subacute/late ones (proliferation of granulation tissue with predominance of myofibroblasts or endothelial cells, resorptive pseudogantomathous granulomas, formation of sarcoid-like granulomas, capsular pseudoinvasion and scarring). Pathologists should be informed about the previously performed FNAC and must be aware of these lesions to prevent their misinterpretation.

        Key words: thyroid gland - fine needle aspiration cytology - postaspiration changes - necrosis - myofibroblast - sarcoid-like granuloma