Perineural Invasion in Salivary Gland Carcinomas in Relation to Tumor Grade and Histological Subtypes

Objectives: Perineural invasion (PNI) in salivary gland carcinomas is a worrying condition that permits tumor cells to travel into and along nerves. The aim of this study was to examine the significance of perineural invasion as measured by H&H, S100, and PGP9.5 and its association with tumor grade and histological subtypes of salivary gland carcinomas, as well as to investigate the role of NGF, NGFR, Galanin in invasion, and metastasis of salivary gland carcinomas. Materials and Methods: A total of 50 paraffin-embedded tissue blocks from the archives of Oral and Maxillofacial Pathology/College of Dentistry/University of Baghdad, Ghazi Al-Harerri Hospital-Medical City from 2000-2021 diagnosed as salivary gland carcinomas and examined histopathologically and immunohistochemically for perineural invasion using S100, PGP9.5, NGF, NGFR, and Galanin in this process (Abcam). Results: 39 (78%) cases of salivary gland carcinomas had perineural invasion. PGP9.5 and S100 recognized perineural invasion more accurately than H and E. Specificity of PGP9.5 higher than that of S100. There was an association between perineural invasion with tumor grade and histological subtypes. Invasion is highly associated with H&E, S100, PGP9.5, NGF, and GAL. There was a significant association between NGF, NGFR, and Galanin. Conclusion: Perineural invasion is associated with tumor grade and histological subtypes and is a predictive factor for tumor development and metastasis. PGP9.5 immunostaining increased PNI detection when compared with H&E and S100. PGP9.5 might be used instead of S-100 to identify PNI or as part of an immunostaining panel for PNI detection. NGF, NGFR, and Galanin may induce tumor cell dispersion and migration, thereby boosting perineural invasion and aiding invasion and metastasis of salivary gland carcinomas.