Investigation of myoepithelial cell differentiation into Schwann-like cells in salivary adenoid cystic carcinoma associated with perineural invasion

Perineural invasion (PNI) is common in salivary adenoid cystic carcinoma (SACC). The aim of the present study was to explore the association of the Schwann-like cell differentiation with PNI in SACC. Twenty-eight cases of SACC and 10 cases of acinic cell carcinoma (ACA) were examined for the expression of the Schwann cell markers Leu-7 by immunohistochemical staining. The correlation between Leu-7 expression and PNI was analyzed using K analysis. Immunofluorescence double-staining and pre-embedding immunogold-silver cytochemistry were used to detect the co-expression and the location of Leu-7 and the myoepithelial cell marker alpha-smooth muscle actin (alpha-SMA). PNI was identified in 16 SACCs (57.1%) and 1 ACA (10%) and the overexpression of Leu-7 was detected in 22 SACCs (78.6%) and in none of the ACAs (0%). The differences between PNI and Leu-7 expression in SACC and ACA were significant (P<0.05). A correlation was identified between the expression of Leu-7 and PNI in SACC (kappa=0.533, P=0.01). In SACC, Leu-7 and a-SMA were co-expressed in the cytoplasm in the same myoepithelial cells. We suggest that Schwann-like cell differentiation correlates with PNI in SACC and that the differentiation of myoepithelial into Schwann-like cells may be one of the mechanisms through which PNI occurs in SACC.