Abstract: Objective To study the expression of midkine(MK) in salivary adenoid cystic carcinoma(SACC) and its relationship with perineural invasion(PNI). Methods Immunohistochemistry staining(SP method) for MK was performed on 35 SACC and 20 normal salivary gland tissues(NSG). Then， the correlation between the expression of MK and PNI was analyzed. Results In SACC， MK was highly expressed and the positive rate was 82.9%（29/35）while it was lowly expressed and the positive rate was 10.0%（2/20）in NSG， which showed significant difference (P<0.01). There was no relationship between the expression of MK and age， sex， pathologic types (P>0.05). However， there was significant difference between PNI cases and nonPNI cases(P<0.05). Conclusions MK may be associated with generation of SACC， and its overexpression may be contributed to the perineural invasion in SACC patients.

Key words: midkine, salivary adenoid cystic carcinoma, perineural invasion, immunohistochemistry