PCSK6 and thyroid gland papillary carcinoma: Finally, as to the histochemical distribution, it is interesting to mention that the apical positivity of PACE4-FL, particularly marked for papillary carcinoma (Fig. 5a), is consistent with data by Couture et al. [13] and Nour et al. [28], suggesting that PACE4-FL is readily reaching the cell surface and accumulating in the extracellular matrix.