Y. Aratake, K. Marutsuka, K. Kiyoyama, T. Kuribayashi, T. Miyamoto, K. Yakushiji, S. Ohno, Y. Miyake, T. Sakaguchi, T. K. Kobayashi, A. Okayama, K. Tamura and E. Ohno
EMMPRIN (CD147) expression and differentiation of papillary thyroid carcinoma: implications for immunocytochemistry in FNA cytologyObjective:  Extracellular matrix metalloproteinase inducer (EMMPRIN) and its induced matrix metalloproteinases (MMPs) play a crucial role in tumour progression, invasion and metastasis. EMMPRIN expression has been demonstrated in several tumours, but its expression profile in thyroid cancer remains unclear.Methods:  We evaluated the expression profile of EMMPRIN at various stages of differentiation of thyroid carcinoma, including 20 cases of well‐differentiated papillary carcinoma (WDPC), 15 cases of papillary carcinoma with a poorly differentiated carcinoma component (PC/PDC) and four cases with an undifferentiated carcinoma (UDC) component, using paraffin‐embedded sections for immunohistochemical stains. Also, we used 32 fine needle aspiration cytology and imprint smears from the same cases for immunocytochemical stains. The staining results were evaluated with a scoring system.Results:  Immunohistochemical staining showed that EMMPRIN expression was absent or weak in almost all WDPC specimens, whereas it was moderate or strong in PDC and UDC components. In tumours that showed a gradual morphological transformation from WDPC to PDC components, the expression of EMMPRIN was progressively stronger from the areas of WDPC to those of PDC. WDPC, PC/PDC and UDC had expression scores of 4.9, 45.0 and 245.7, respectively. Results of immunocytochemical staining showed almost the same staining profile as those of immunohistochemical staining. The cytological atypia of EMMPRIN‐positive cells was greater than that of negative cells.Conclusion:  These results indicated that EMMPRIN expression correlates significantly with the degree of dedifferentiation of thyroid carcinoma. This study demonstrates the feasibility of expression of EMMPRIN using fine needle aspiration samples. Therefore, immunocytochemical analysis of EMMPRIN may be a novel aid to evaluate the differentiation of thyroid carcinoma.