In this study, we report a 37-year-old female followed by the MEN clinic of the Federal University of Sao Paulo (UNIFESP) who presented a thyroid nodule with cytological results indicative of Hürthle cell neoplasm and an extremely high calcitonin level (2079 pg/ml, normal=8.5/5.0 pg/ml). The gene discussed is CALCA; the disease is thyroid nodule.