A Histopathologic Scoring System for Perineural Invasion Correlates With Adverse Outcomes in Patients With Cutaneous Squamous Cell Carcinoma.

Background: Perineural invasion (PNI) is a known risk factor for recurrence, metastasis, and death in cutaneous squamous cell carcinoma (cSCC). Current staging systems include PNI, but none define its extent or severity.
Objective: To identify histopathologic features of cSCC with PNI that may be associated with adverse outcomes.
Materials and Methods: This is a retrospective cohort study that included 45 patients with cSCC and PNI treated with surgical excision. Histopathologic slides were analyzed for 5 features of PNI: largest affected nerve diameter, number of nerves affected, depth of nerve involvement, intra- versus extratumoral PNI, and focal versus circumferential PNI.
Results: The median largest affected nerve diameter was 0.13 mm, and the median number of nerve structures involved was 4. After a median follow-up time of 24 months, 6 patients developed adverse outcomes, including 2 local recurrences, 4 metastases, and 2 tumor-related deaths. Univariate logistic regression analysis revealed that nerve diameter and number of affected nerves were significantly associated with adverse outcome. A composite PNI score, calculated from 5 histopathologic features, was the strongest predictor of adverse outcome (p = .020).
Conclusion: Histopathologic features of PNI can be quantified with a composite PNI score that is significantly associated with adverse outcomes in cSCC.
(Copyright © 2021 by the American Society for Dermatologic Surgery, Inc. Published by Wolters Kluwer Health, Inc. All rights reserved.)