Anal metastasis from rectal adenocarcinoma

The metastasis of rectal cancer to the anus is rare. Here, we report a case of advanced rectal cancer, which had a diffuse venous invasion with anal metastasis and multiple lymph node and liver metastases. The patient was a 72-year-old woman who complained of perianal pain and fresh blood in the stools for 6 months. She had neither history of fistula-in-ano nor anal surgery. Digital examination revealed a 2-cm tumor at the 7 o'clock position, and the barium enema and colonoscopy confirmed advanced rectal cancer. Abdominal computed tomography revealed thickness of the upper rectum wall, right inguinal lymph node of 10 mm and multiple liver metastases. Laparoscopically assisted anterior resection, anal tumor resection, and right inguinal lymph node resection were performed, and the histopathological examination of the resected primary and metastatic tumors confirmed similar findings of moderately differentiated adenocarcinoma, suggestive of metastasis of the rectal cancer to the anal region. In the next procedure, she had the liver lesions resected. This case suggested the importance of the careful examination of the anus during colonoscopy, or digital examination for the detection of anal metastasis.