A case of metastatic carcinoma of anal fistula caused by implantation from rectal cancer.

Rina Takahashi,Singo Ito,Shun Ishiyama,Yuichi Tomiki,Ryosuke Ichikawa,Kazuhiro Sakamoto,Michitoshi Goto,Kosuke Mizukoshi,Kiichi Sgimoto,Takashi Yao,Yutaka Kojima

doi:10.1186/s40792-015-0125-2

Abstract

This case involved an 80-year-old man who was seen for melena. Further testing revealed a tubular adenocarcinoma 50 mm in size in the rectum. In addition, an anal fistula was noted behind the anus along with induration. A biopsy of tissue from the external (secondary) opening of the fistula also revealed adenocarcinoma. Nodules suspected of being metastases were noted in both lung fields. The patient was diagnosed with rectal cancer, a cancer arising from an anal fistula, and a metastatic pulmonary tumor, and neoadjuvant chemotherapy was begun. A laparoscopic abdominoperineal resection was performed 34 days after 6 cycles of mFOLFOX-6 therapy. Based on pathology, the rectal cancer was diagnosed as moderately differentiated adenocarcinoma, and this adenocarcinoma had lymph node metastasis (yp T3N2aM1b). There was no communication between the rectal lesion and the anal fistula, and a moderately differentiated tubular adenocarcinoma resembling the rectal lesion was noted in the anal fistula. Immunohistochemical staining indicated that both the rectal lesion and anal fistula were cytokeratin 7 (CK7) (−) and cytokeratin 20 (CK20) (+), and the patient’s condition was diagnosed as implantation of rectal cancer in an anal fistula.In instances where an anal fistula develops in colon cancer, cancer implantation in that fistula must also be taken into account, and further testing should be performed prior to surgery.

Highlights

A handful of studies have reported primary cancer arising from a chronic anal fistula [1], but implantation of tumor cells in an anal fistula is rare
The patient’s condition was diagnosed as rectal cancer, a cancer arising from an anal fistula, and a metastatic pulmonary tumor, and neoadjuvant chemotherapy (NAC) was initiated with 6 cycles of mFOLFOX-6 therapy
In cases previously encountered by the current authors, this cancer had a histologic type resembling colon cancer, and immunohistochemical staining indicated that both the lesion and the fistula stained negative for cytokeratin 7 (CK7) and positive for cytokeratin 20 (CK20)

Summary

Background

A handful of studies have reported primary cancer arising from a chronic anal fistula [1], but implantation of tumor cells in an anal fistula is rare. The current authors encountered a case in which cancer cells migrating from rectal cancer were implanted in an anal fistula. A mass was not palpated during a rectal examination, but the external opening of an anal fistula was noted behind the anus (Fig. 1a). The patient’s condition was diagnosed as rectal cancer, a cancer arising from an anal fistula, and a metastatic pulmonary tumor, and neoadjuvant chemotherapy (NAC) was initiated with 6 cycles of mFOLFOX-6 therapy. After NAC, a CT scan revealed reduced thickening of the rectal wall and shrinkage of mesorectum lymph nodes Nodules in both lung fields shrank, and tumor shrinkage according to the RECIST criteria was 34 %. New metastases have not been noted, and there has been no change in the lung metastases and patient’s status

Findings

Discussion

Conclusions