Comparison of epi-tumoural lymphatic vessel density, lymphovascular invasion, shields index and sentinel lymph node biopsy. Shields Index values were calculated on primary tumours from SNLB patients A) Mean epi-tumoural LD (p < 0.01, unpaired t test). B) Percentage of patients that were positive for LVI (p > 0.05, Fisher's Exact Test). C) Mean Shields Index values (p < 0.001, unpaired t test) for SLNB positive and negative patients. Error bars represent standard error of the mean.