['Haem oxygenase-1 (HO-1) is an inducible enzyme that participates in haem degradation. Recent studies have indicated that HO-1 activation may play a role in tumour development and progression. The aim of this study was to evaluate the expression of HO-1 in thyroid cancer and its clinicopathological significance.', 'We observed up-regulation of HO-1 in papillary thyroid tumours in comparison with normal thyroid tissue. Immunohistochemical analysis revealed that 48% of papillary cancers and 36% of follicular cancers, but none of normal thyroid tissues, were positive for HO-1 expression. Among 129 differentiated thyroid cancers, HO-1 expression was associated with patient age (P = 0.001), TNM stage (P = 0.001), and Mayo Clinic metastasis, patient age, completeness of resection, local invasion and tumour size score (P = 0.001). BRAF V600E expression was evaluated immunohistochemically and validated by Sanger sequencing. There was a strong association between HO-1 and BRAF V600E expression in papillary cancers (P = 0.002).'] Does expression of haem oxygenase-1 correlate with tumour aggressiveness and BRAF V600E expression in thyroid cancer?