Perineural invasion (PNI) in vulvar carcinoma: A review of 421 cases

Objectives: To evaluate the prevalence and associated prognostic indicators in patients with vulvar carcinoma with and without evidence of perineural invasion (PNI). Methods: A retrospective review identified 421 patients with invasive vulvar carcinoma evaluated at a single institution between 1993 and 2011. Medical records were reviewed for demographic data, pathologic information and presence or absence of PNI, treatment type, and recurrence/outcome information. Variables were compared between patients with PNI to those without PNI. Results: Of the 421 patients included in the study, 32 (7.6%) had tumors with PNI. There were no significant differences in age, race/ethnicity, smoking history, histologic subtype, or grade between the group of patients with PNI and the group without PNI. The group with PNI was more likely to have lichen sclerosus (25.0% vs. 15.4%, p = 0.024), stage III/IV disease (59.4% vs. 36.0%, p = 0.007), lymph node involvement (50.0% vs. 21.6%, p = 0.002), and lymphovascular space invasion (LVSI) (53.1% vs. 15.9%, p < 0.001). A higher proportion of patients in the PNI group underwent primary or adjuvant radiation therapy (68.8% vs. 45.0%, p = 0.016). The median follow-up was 67.1 months (range < 1.0 to 284.3). Patients with PNI had significantly shorter overall survival (OS), median 25.5 vs. 94.3 months (p < 0.001), and progression-free survival (PFS), median 17.5 vs. 29.0 months (p = 0.004). After adjusting for stage, patients with PNI had a greater risk for death and progression (OS: hazard ratio, 2.71; p < 0.001; PFS: hazard ratio, 1.64; p-value = 0.020). Conclusion: PNI should be considered an independent poor prognostic factor for patients with vulvar carcinoma, and should be included as part of the pathologic analysis.