Hai-Xia Fan,1 Yan Chen,1 Bo-Xiong Ni,1 Shan Wang,1 Miao Sun,2 Dong Chen,2 Jin-Hua Zheng11Department of Anatomy, Basic Medical Science College, 2Department of Oral and Maxillofacial Surgery, Stomatological Hospital, Harbin Medical University, Harbin, People’s Republic of ChinaBackground: Matrix metalloproteinase (MMP)-1 degrades type I collagen of the extracellular matrix and also activates protease activated receptor (PAR)-1 to induce angiogenesis. The aims of this study were to evaluate microvessel density (MVD) and the expression of PAR-1 and MMP-1 in oral squamous cell carcinoma (SCC) specimens with different patterns of invasion (POI) and to evaluate their association with clinical outcomes.Methods: Seventy-four surgically obtained oral SCC samples were classified by POI according to hematoxylin-eosin staining. MVD and the localization and intensity of PAR-1 and MMP-1 expression were detected by immunohistochemistry.Results: Of the 74 oral SCC samples, 18, 5, 34, and 17 showed type I, II, III, and IV POI, respectively. MVD and expression levels of MMP-1 and PAR-1 differed between POI types I–II and POI types III–IV. Patients with low tumor expression of MMP-1 and PAR-1 and low MVD had a longer survival time than those with high tumor expression of MMP-1 and PAR-1. Moreover, the survival time of patients with POI types III–IV was shorter than that of patients with POI types I–II.Conclusion: POI combined with expression levels of MMP-1 and PAR-1 may be a valuable tool for assessing the clinical prognosis of patients with oral SCC.Keywords: oral squamous cell carcinoma, pattern of invasion, immunohistochemistry, clinical outcomes