Complications following fine needle aspiration (FNA) are very infrequent and generally resolve spontaneously without treatment. The appearance of necrosis or infarction after FNA of the thyroid gland is an exceptional finding. An 83-year-old woman with a thyroid nodule was subjected to diagnostic FNA using a G23 needle. The patient noted a decrease in nodule size after FNA. A total thyroidectomy was performed 36 days after FNA. The cytological diagnosis was papillary carcinoma. Histology revealed massive coagulation necrosis affecting 80% of the tumor mass; the cytological diagnosis was confirmed. Iron pigment deposits were observed in the vicinity of the necrotic areas together with interstitial fibrosis; this suggested a mechanism of ischemic necrosis but no vascular thrombosis was observed. Post-FNA tumour regression of a thyroid lesion is an infrequent finding thet should be made known to clinicians and pathologist, since final diagnosis may be difficult by the massive necrosis.