-Case Reports-

Squamous Cell Carcinoma Arising from Recurrent Anal Fistula

Tomoko Seya^1,2, Noritake Tanaka^1,2, Seiichi Shinji^1,2, Kimiyoshi Yokoi^1,2, Tatsuo Oguro³, Yoshiharu Oaki³, Toshiyuki Ishiwata⁴, Zenya Naito⁴ and Takashi Tajiri¹

¹Surgery for Organ Function and Biological Regulation, Graduate School of Medicine, Nippon Medical School
²Department of Surgery, Nippon Medical School Chiba Hokusoh Hospital
³Department of Pathology, Nippon Medical School Chiba Hokusoh Hospital
⁴Department of Integrative Pathology, Graduate School of Medicine, Nippon Medical School

Here, we report on a patient with squamous cell carcinoma (SCC) arising from recurrent anal fistula. The patient was a 57-year-old woman who had 32-year history of having a recurrent perianal abscesses that ruptured spontaneously. Six months before her admission to our hospital, anal pain developed. She had no history of inflammatory bowel disease. Physical examination revealed three external fistulous openings at the two o'clock position, 2 cm from the anal verge. One internal opening in the lower rectum was found with proctoscopy. The patient underwent fistulectomy. Microscopic examination showed SCC arising from the anal fistula, which was accompanied by vessel invasion. The tumor was observed to be continuous from the external opening but was not exposed to the internal opening of the rectal mucosa. Because human papillomavirus (HPV) infection was suspected, immunohistochemical analysis was performed, but showed no HPV infection. Two weeks after fistulectomy, abdominoperineal resection with lymph node dissection was performed. Histopathological examination revealed no remnant cancer tissue or lymph node metastasis. She was discharged after surgery without complications. Eight years after the operation, she complained of constant pain during micturition. Urological examination revealed urinary bladder cancer, and transurethral resection of the bladder tumor was performed. Histopathological examination revealed transitional cell carcinoma of the urinary bladder. Two years later, the patient died of metastatic urinary bladder cancer, without recurrence of the fistula cancer. Because the patient's mother had died of urinary bladder cancer and she herself had metachronous urinary bladder cancer in addition to fistula cancer, we investigated whether microsatellite instability (MSI) and chromosomal instability correlated with fistula cancer development. Immunohistochemical analysis of formalin-fixed, paraffin-embedded surgical tumor specimens for p53, MLH1, and MSH2 was performed. The tumor specimens showed no MLH1 expression but did show normal MSH2 expression. p53 was not expressed. Five microsatellite loci were examined using the tumor specimens to detect MSI, namely two loci with mononucleotide runs (i.e., BAT25 and BAT26) and three loci with dinucleotide repeats (i.e., APC, Mfd15, and D2S123). The tumor specimens showed alternations in the repeated sequences of two loci (i.e., BAT26 and D2S123). As a result, the tumor was classified as MSI-H (high) according to the Bethesda criteria. Our patient had MSI and one of the smallest reported SCCs arising from recurrent anal fistulae.

J Nippon Med Sch 2007; 74: 319-324

Keywords
anal fistula, squamous cell carcinoma, microsatellite instability, chromosomal instability, human papillomavirus

Correspondence to
Tomoko Seya, MD, Ph D, Department of Surgery, Nippon Medical School Chiba Hokusoh Hospital, 1715 Kamagari, Inbamura, Inba-gun, Chiba 270-1694, Japan
seya@nms.ac.jp

Received, April 9, 2007
Accepted, May 14, 2007