Prevalence and significance of perineural invasion in invasive breast carcinoma

Lymphovascular invasion (LVI) is a poor prognostic feature in breast cancer. Perineural invasion (PNI), a sign of aggressive behavior potential in other tumor systems, is less frequently observed in mammary carcinoma and hence has been less well studied. The present work was conducted to determine the frequency of PNI in mammarycarcinoma and to describe the relationships between PNI, tumor characteristics (including LVI) and clinical outcome.

The Hartford Hospital pathology database was reviewed for cases of invasive mammary carcinoma diagnosed from 2000-2002. The search was then narrowed to include only those cases reporting PNI, LVI, or both. These targeted reports were then reviewed to abstract clinicopathologic data with regard to patient age, tumor stage and nuclear/ histologic grade. Histologic review was performed on all PNI(+)cases. Comparisons between tumor characteristics associated with PNI and LVI were generated. Nodalstatus andpatientoutcomewereobtainedfrom cancer registry records.

From a total of 1136 cases of invasive mammary carcinoma diagnosed from 2000-2002, 13 (1.14%) and 146 (12.9%) showed PNI and LVI, respectively. Of the 13 patients with PNI, 5/13 (38.5%) also had LVI. Both PNI and LVI were associated with higher T-stage and intermediate to high NG/HG.

PNI is a relatively rare histologic feature in invasive breast carcinoma occurring 10 times less frequently than LVI. Tumor characteristics associated with PNI include higher T-stage, higher tumor grade and LVI. Despite this, patients with PNI can expect a meaningful survival at five years with appropriately aggressive adjuvant therapy (only one of 13 patients in this study was known DOD after mean follow-up of 5.9 yr). When observed in tissue sections PNI should be reported (for completeness) but its role as an independent poor prognostic feature remains questionable.