PMC

The association between perineural invasion and ESCC patients’ survival (log-rank test). Kaplan-Meier survival analysis of perineural invasion for overall survival (A) and recurrence-free survival (B) in ESCC patients.

Univariate survival analysis with regard to perineural invasion in the subset of ESCC patients with node-negative disease. The presence of perineural invasion was identified as a prognostic predictor of overall survival (A) and recurrence-free survival (B) in ESCC patients with node-negative disease.

The status of perineural invasion (PNI) in ESCC specimens. Tumor cells located within any of the endoneurium (A), perineurium (B) and epineurium (C) of the peripheral nerve sheath are clear examples of PNI. When tumor cells are not located inside of the nerve sheath but are in close proximity to the nerve in the perineural environment, at least 33% of the circumference of the nerve should be surrounded by tumor cells to diagnose PNI (D); anything less than 33% represents focal abutment and not invasion (E). When tumor cells are not in close proximity to the nerve in the perineural environment (F), it represents negative finding (hematoxylin-eosin staining, ×100).