The Comparative Evaluation of Perineural Invasion and Vascular Invasion in Adenoid Cystic Carcinoma and Mucoepidermoid Carcinoma of Salivary Glands by Expression

Mucoepidermoid carcinoma (MEC) and Adenoid cystic carcinoma (AdCC) are the most common salivary malignancies, and their biologic behavior has not been completely determined. Perineural and vascular invasion are effective on the biologic behavior. Therefore, the aim of this study was to evaluate perineural and vascular invasion in AdCC and MEC of major and minor salivary glands by expression of neural markers such as S-100, GFAP, NCAM and vascular marker such as PECAM-1. Formalin-fixed and parafin-embedded tissue sections of 20 cases of AdCC and 20 cases of MEC were immunohistochemically analyzed for the presence of S-100, GFAP, NCAM, PECAM-1by biotin streptavidin Novolink polymer procedure after antigen retrieval. Data were analyzed by Mann-Whitney and Fisher's exact tests. All AdCCs and MECs were positive (+1→+4) for S-100. S-100 positive frequency and severity ratios in AdCC were higher than MEC (P<0.05). Two specimens of AdCC and nine specimens of MEC were positive (+1) for GFAP. GFAP positive frequency and severity ratios in MEC were higher than AdCC (P=0.013). All AdCCs and MECs were negative for NCAM and PECAM-1 (P=1). The presence of S-100 and GFAP in AdCC and MEC probably indicates the role of myoepithelial cells in histogenesis of theses tumors. Considering that perineural invasion in salivary gland tumors has been ascribed to myoepithelial cell, this characteristic does not necessarily indicate the poor prognosis of these tumors. As a result, according to the lack of expression of NCAM and PECAM-1 in AdCC and MEC and other findings, perineural and vascular invasion in these tumors do not appear to be different significantly.