[Clinicopathological studies on perineural invasion of rectal cancer with special reference to the prognosis and nerve preserving operation].

Prospective studies on rectal cancer have been continued since 1982 in our department and in the present study, the significance of perineural invasion was investigated clinicopathologically in 432 cases of rectal cancer. (1) Perineural invasion in rectal cancer appeared to be closely related to the degree of progress of the cancer (depth of penetration, lymph node metastasis, liver metastasis and peritoneal dissemination), the degree of malignancy of the cancer (histologic type, lymphatic invasion and venous invasion) and the degree of inflammatory cell infiltration. (2) It was proven to be an important prognostic factor which influences recurrences and the survival rate. (3) If cases indicated for nerve preserving operation are considered to be those with no perineural invasion or with a low frequency of such invasion, it was assumed that such cases are those with well differentiated adenocarcinoma, a penetration depth of ss (a1) or less and no lymph node metastasis.