[Pathological analysis of low rectal malignancy and preservation of anus].

The specimens from 56 low rectal malignancy patients (tumor within 6 cm of anorectal line) who received Miles' operation were pathologically studied. The invasion of sphincter ani had no relation to involvement of the rectal circumference or gross type of the tumor, but was related to the distance between tumor and anorectal line and tumor differentiation. Of 35 patients with tumor 0-3 cm from anorectal line, the sphincter ani was involved in 15 but none in 21 patients with tumor 3.1-6cm from anorectal line (P less than 0.01). There were 1 well-differentiated and 5 poorly-differentiated adenocarcinomas in 15 patients with invasion of sphincter ani, the difference therein was significant (P less than 0.01). The authors suggest that resecting low rectal malignancy but preserving the anus be given to patients with well-differentiated tumors 4-6 cm above the anorectal line.