Perineural and lymphovascular invasion in squamous cell carcinoma of the tongue.

BACKGROUND Perineural invasion (PNI) and lymphovascular invasion (LVI) may be adverse prognostic indicators in squamous cell carcinoma (SCC) of the tongue. METHODS The percentages of histological PNI and LVI were determined in 335 patients with tongue SCC. Sixty tumours originally reported as negative for these features were tested to determine how many more were positive with "immunohistochemical enhancement." RESULTS PNI was found in 141 (42.1%) and LVI in 51 (15.2%) patients. 79.4% of the 141 patients who had PNI and 72.6% of the 51 with LVI had a T3 or T4 tumour. Lymph node metastasis was identified in 145 (51.2%) of the 280 patients who had undergone neck dissection; 58.2% of the 141 patients with PNI and 80.4% of the 51 patients with LVI had lymph node metastasis. There was a highly statistically significant correlation between PNI with increasing pT (P < .00001) and pN (P < .0001) stage, and a statistically significant correlation between LVI and pT stage (P < .001), the association of LVI with pN status could not be reliably tested statistically. Immunohistochemistry for S100 identified five further cases of PNI, but review of the original H&E showed the feature was present in four and had been missed at original reporting. CD31 identified three further possible cases of LVI and D2-40 none. The endothelium of some vascular channels was positive for both CD31 and D2-40 and cross-reactivity with other cells compromised interpretation. CONCLUSIONS Histological identification of PNI and LVI per se remains of uncertain prognostic significance. "Immunohistochemical enhancement" offered little benefit.