Perineural invasion has no prognostic value in patients with invasive breast carcinoma.

No studies examining the relationship between perineural invasion (PNI) and clinicopathological factors in invasive breast cancer have been published. Therefore, we investigated this association and analyzed the effect of PNI on disease-free survival (DFS) in patients with invasive breast carcinoma. PNI evaluation was performed on hematoxylin- and eosin-stained tissue sections of surgical specimens from 377 patients. PNI was assessed as positive when cancer cells were seen in the perineurium or neural fascicles. PNI was found in 97 out of 377 patients (25.7%). PNI positivity was 13.9% in T1 tumors and 69.7% in T4 tumors (P<0.001). The incidence of PNI was higher in ductal and mixed type carcinomas than in other histologic types (P=0.013). Vascular invasion, axillary lymph node and progesterone receptor positivity ratios were significantly higher in PNI-positive patients than in PNI-negative ones (P<0.001, P=0.001 and 0.006, respectively). There was no difference between PNI-positive and -negative patients regarding DFS. In conclusion, in invasive breast carcinomas, PNI incidence is lower in small and axilla-negative tumors, and higher in ductal and mixed type and hormone-sensitive tumors; PNI has no prognostic importance.