Hereby, we present a study analysing COX-1 and COX-2 expression in papillary thyroid carcinoma (PTC), Hashimoto thyroiditis (HT) and nontoxic nodular goitre (NNG) in fine needle aspiration biopsy (FNAB) washouts and in postoperative tissue. Here, PTGS1 is linked to Hashimoto thyroiditis.