Anal Fistula Cancer Associated With Crohn'S Disease: Report Of A Case

Background: Anal canal is often involved in Crohn's disease (CD), and intractable anal fistula is frequently associated with CD. Recent studies show that the risk of colorectal cancer is increased in patients with CD colitis. Therefore, it is suggested that the risk of anal fistula cancer is elevated. The prognosis of anal fistula cancer associated with CD is generally poor, and its natural course has not been clarified yet. Methods: A Japanese man was referred to our hospital because he was diagnosed as rectal cancer associated with CD. When his first symptoms of CD were recognized, he was 25 years old. After 13 years, he received subtotal colectomy and ileo-sigmoid colon anastomosis for entero-entero fistula. He received maintenance therapy with azathioprine and infliximab, and continued for 9 years, when he got his anal fistula deterioration, and he received drainage of perianal abscess. Results: On the other hand, annual surveillance colonoscopy was performed for several years. Three years before the diagnosis of cancer, a small reddish, slightly depressed area was recorded very close to the dentate line. In the next year, the lesion looked larger and more raised. It got even more protuberant, but the size looked almost the same in the following year. Finally, it developed in size and the surface pattern suggested neoplasm, and it was biopsied for the first time, which revealed high grade dysplasia. He agreed excisional biopsy under spinal anesthesia. At operation, the tumor was excised firstly. A primary orifice of anal fistula was located very close to the tumor. After we sterilized the surrounding area with povidone iodine and changed gloves and instruments to avoid contamination, we explored the fistula with curettage. We also examined the surrounding mucosa separately. The specimens were submitted for pathological review. The tumor was restricted to mucosal layer in the raised lesion, and the specimen from anal fistula included high grade dysplasia. Therefore, we recommended him to receive abdominoperineal resection for possible cancer at the anal fistula, which he agreed. Computed tomography or magnetic resonance imaging revealed no evidence of malignancy. The specimen of abdominoperineal resection showed remaining cancer in the anal fistula. The size was approximately 1 × 2 cm. The histology was consisted of well differentiated adenocarcinoma and mucinous adenocarcinoma. Conclusions: We present a case of anal fistula cancer and rectal dysplasia associated with Crohn's disease. The molecular status of the 2 tumors might be of help to reveal the association between them.