A case of
mucinous adenocarcinoma arising on a long-standing anorectal
fistula is described. A 60-year-old man with a long history of mucinous discharge,
pain and perianal induration underwent a biopsy of the external opening of the
fistula that showed a mucinous infiltrating
adenocarcinoma. Due to the large size of the
tumor and the fact that it had extended into the surrounding tissue, preoperative
radiotherapy was performed.
Radiotherapy was given with 40 Gy in 25 fractions for 5 weeks through posterior and bilateral portals. After
radiotherapy the
tumor was markedly shrunk and the serum level of
carcinoembryonic antigen was also improved.
Abdominoperineal resection was performed 8 weeks after the termination of
radiotherapy. Histological examination of the resected specimen revealed that the invasion of the
tumor remained within the sphincter muscle and that no
cancer cells were present on the
surgical margin. The histological effect of
radiotherapy was judged as grade 1b. This treatment can result in downstaging and R0 resection, which also has a possibility to prevent local recurrence. This case suggests that preoperative
radiotherapy may play an important role in the definitive treatment of locally advanced perianal
mucinous adenocarcinoma.