Perineural invasion in pancreatic cancer.

INTRODUCTION: Perineural invasion is regarded as a factor associated with local recurrence of pancreatic cancer. AIM: To examine perineural invasion of pancreatic cancer pathologically and clinically. METHODOLOGY: In 24 cases of surgically resected pancreatic cancer, correlations among the degree of perineural invasion, differentiation, interstitial connective tissue, lymph node metastasis, and survival rate were examined. Consecutive 5-microm serial sections (n = 1072) were made in six cases that showed characteristic mode of perineural invasion. RESULTS: Perineural invasion was observed in 17 cases (70.8%; ne0-7; ne1-6; ne2-9; and ne3-2 cases). Perineural invasion was absent in three of five cases of papillary carcinoma, but was observed in 12 of 14 cases of moderately differentiated carcinoma. The survival rate for ne0 was better than that of the other groups, with the 3-year survival rate being 57.1%. Perineural cancer glands had developed discontinuously in two cases. CONCLUSIONS: Perineural invasion is an important prognostic factor in pancreatic cancer, increasing as the cancer becomes undifferentiated. Even if there are no cancer cells at the margin of the pancreas at the time of surgery, the cancer cells may spread further to the noncancerous pancreas or retroperitoneum. Sufficient dissection of the neural plexus or intraoperative radiation may be required.