perianal mucinous adenocarcinoma is a rare disease often associated with a long - standing anal fistula , representing approximately 23% of large bowel cancers .
the occurrence of a carcinoma in association with a fistula is probably due to chronic inflammation , although the rarity of the condition precludes any definite assumption in regard to the etiologic relationship of the fistula and carcinoma . in most patients , early diagnosis of this disease
detection is usually late as the symptoms often initially mimic benign inflammatory conditions of the anorectal region and biopsies fail to reveal the infiltrating carcinoma . therefore a tumor is often found in progress . due to the rarity of this tumor and the lack of sufficient patients for controlled trials ,
abdominoperineal resection ( apr ) is advocated in the vast majority of patients to definitively remove the entire lesion and lessen the risk of local recurrence .
local resection is sometimes performed , but only in cases where the tumor margins can be confidently excised without damage to the anal sphincters . in order to prevent local recurrence , the apr has to be performed with wide local excision of both perianal soft tissue and the overlying skin .
recently locally advanced rectal cancer has been considered an indication for preoperative chemoradiotherapy ( crt ) .
preoperative crt for rectal cancer has been shown to increase the probability of tumor resectability and to decrease the rate of local recurrence .
radiotherapy alone or combined with chemotherapy can be a curative treatment for squamous cell carcinoma of the anal canal .
on the other hand , the role of radiotherapy has not been established for perianal mucinous carcinoma .
the aim of this article is to report a rare case of large perianal mucinous adenocarcinoma , arising from an anorectal fistula , successfully resected after preoperative radiotherapy .
a 60-year - old man with a 45-year history of perianal fistula who had recently been suffering from mucinous discharge , pain and perianal induration was referred to hospital for treatment .
two years before , he had undergone surgery at another institution for incision and drainage of recurrent perianal abscess .
physical examination revealed an indurated , ulcerative lesion 7 cm in diameter with an external anal fistula opening ( fig .
the internal opening of the fistula was indicated at the right side of dentate line .
magnetic resonance imaging ( mri ) demonstrated a large demarcated tumor at the level of the anorectal junction with extension to the right side of the ischiorectal fossa and presacral space ( fig .
no enlarged pelvic lymph node was observed , nor was there evidence of distant metastasis .
neither colonoscopy nor barium enema showed any evidence of mucosal lesion in the colon or rectum .
laboratory data showed renal dysfunction caused by pyelonephritis , and the carcinoembryonic antigen serum level was extremely elevated to 40.8 ng / ml ( normal < 5 ng / ml ) . to increase resectability and
decrease the rate of local recurrence , preoperative radiotherapy was proposed without chemotherapy because of the renal dysfunction .
preoperative radiotherapy was given with 40 gy in 25 fractions for 5 weeks through posterior and bilateral portals .
1c , d ) and carcinoembryonic antigen serum level gradually decreased to 13.0 ng / ml .
the resected specimen revealed that the tumor had developed in the ischiorectal fossa , but there was no evidence of cancer extension to the mucosal surface of the anal canal and rectum ( fig .
histological examination of the excised specimen showed foci of mucinous adenocarcinoma involving the lower internal and external anal sphincter muscles , and the resected margins did not show any residual tumor ( fig .
3 ) . according to the uicc tnm staging criteria , the treatment outcome with preoperative radiotherapy revealed minimal response ( grade 2 ) .
perianal mucinous adenocarcinomas arising from anorectal fistulae are rare tumors resulting in severe problems concerning diagnosis and treatment .
it is suggested that adenocarcinoma developing in the perianal region is often associated with a long - standing anal fistula
. early diagnosis of a perianal tumor is difficult because of the absence of a tumor within the lumen of the bowel and the slow growth of a lesion hidden within the ischioanal fossa .
as local excision is inadequate in most cases , apr with wide excision of both ischiorectal fossae and the overlying skin is recommended . on the other hand , radiotherapy alone or
combined with chemotherapy can be a curative treatment for squamous cell carcinoma of the anal canal . in the present case ,
total removal of the tumor without any residual tumor was quite difficult because of the size of the tumor and the fact that it had infiltrated the surrounding tissue .
recently , preoperative crt has become common practice for stage ii and iii rectal cancers .
it has been well documented that neoadjuvant crt induces tumor regression and downstaging , and therefore increases tumor resectability and r0 resection rate .
therefore we performed preoperative radiotherapy to improve the resection rate and decrease the local recurrence rate .
after treatment the tumor was markedly shrunk and could be completely resected without skin grafting .
this suggests that preoperative radiotherapy with or without chemotherapy is appropriate for treatment of perianal mucinous carcinoma arising from an anorectal fistula if adequate surgical margins can not be ensured .
the role of crt in the treatment of perianal mucinous adenocarcinoma has not yet been established .
unfortunately there are an insufficient number of reported cases undergoing this therapy to determine the prognosis for individual patients [ 7 , 8 ] .
further tests are required to standardize the treatment of preoperative crt for locally advanced perianal mucinous adenocarcinoma arising from an anorectal fistula . in conclusion ,
if surgical treatment for anorectal fistula is unsuccessful in the long term , mucinous adenocarcinoma should be suspected .
the result of this case suggests that preoperative radiotherapy appears to be a valuable alternative treatment for patients with perianal mucinous adenocarcinoma arising from an anorectal fistula . the advantage of this approach can result in downstaging and r0 resection , which prevents local recurrence .
 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 . 
Introduction
Case Report
Discussion