Strong expression of HBME-1 associates with high-risk clinicopathological factors of papillary thyroid carcinoma

Thyroid cancer comprises a heterogeneous group of lesions with great diversity of biological behaviour. Markers which could help clinicians to identify high-risk patients for tailored optimization of clinical management are of crucial importance. HBME-1 protein level was analysed immunohistochemically using routinely prepared archival tissue sections of a broad range of papillary thyroid carcinoma (PTC) variants and in corresponding lymph node metastases (LNM). The results were evaluated in comparison with clinicopathological features of PTC. Positive immunoreaction was noticed in most classical (83/92; 90.2 %), follicular (60/71; 84.5 %) and trabecular (4/5; 80.0 %) variants of PTC. All cases of macrofollicular, Warthin-like and diffuse sclerosing PTC variants were HBME-1 positive (4/4, 3/3, 2/2; 100 % respectively). Tall cell and solid PTC variants showed diversity of staining (2/3; 66.67 % and 13/23; 56.52 % respectively), while PTCs with mixed histological pattern containing insular areas were mainly weakly positive (2/5; 40.0 %). A single case of clear cell PTC variant showed no reaction. Moreover, all matched metastatic PTC into lymph nodes (LNM) were HBME-1 positive (17/17; 100 %) and expressed HBME-1 in a similar pattern to the matched primary tumour. We also found a statistically significant association between high HBME-1 expression and the presence of lymph node metastasis, advanced pT status and pTNM stage (P < 0.05), but only a tendency for association with extrathyroidal invasion of the tumour (P = 0.058). Therefore, we recommend using immunoexpression of HBME-1 as useful mean to increase the likelihood of detecting most PTC variants and to predict some unfavourable clinical parameters in these patients.