Diagnostic accuracy of perineural invasion in oral squamous cell carcinoma is improved by immunohistochemistry and correlates with locoregional recurrence.

Aims: In oral squamous cell carcinoma (OSCC), we investigated whether perineural invasion (PNI) and cell proliferation are associated with locoregional metastasis and recurrence. Settings and Design: Thirty-nine cases of OSCC were included in this retrospective study. Materials and Methods: Clinical-histopathological data were obtained from medical records. New slides were performed, and PNI status was assessed using hematoxylin and eosin-stained (H&E) and immunostaining for S100. PNI was described as tumour cells infiltrating >33% of the nerve circumference, complete nerve encirclement or intraneural infiltration. The status of proliferation was assessed by immunohistochemistry using Ki-67. Statistical Analysis Used: PNI and cell proliferation were associated with OSCC outcomes by univariate and multivariate regression. Results: PNI was positive in 17.9% H&E cases, increasing to 51.2% immunostaining (S100) analysis (0.004). All PNI-positive patients were ≤50 years. Intraneural invasion was the most common PNI-positive feature, followed by complete encirclement. All PNI-positive cases with locoregional recurrence showed intraneural invasion (0.001). PNI-positive tumours were most common in the soft palate and oropharyngeal subsites (66.7%), and smokers + alcoholics represented 80.0% of all PNI-positive cases. N0 and M0 tumours represented most PNI-positive cases. High cell proliferation represents an increased risk of PNI and is associated with lymph node metastasis in OSCC (0.001). Conclusions: S100 immunohistochemistry is useful to improve the diagnostic accuracy of PNI in OSCC by reducing the alpha and beta errors. PNI is common in OSCC, and PNI S100 diagnosis correlates with locoregional OSCC recurrence. High cell proliferation (Ki-67) was useful in predicting lymph node metastasis.