Metachronous tubulovillous and tubular adenomas of the anal canal

Abstract

Anal canal adenoma is an extremely rare disease that has the potential to transform into a malignant tumor. We herein presented a rare case of metachronous multiple adenomas of the anal canal. A 48-year-old woman underwent total colonoscopy following a positive fecal blood test. A 9-mm villous polyp arising from the posterior wall of the anal canal was removed by snare polypectomy. Histologically, the tumor was tubulovillous adenoma with high-grade dysplasia and the cut end was negative for tumor cells. Six years later, an elevated lesion, macroscopically five millimeters in size, was detected in the left wall of the anal canal in a follow-up colonoscopy. Local excision of the tumor was performed, and the lesion was pathologically confirmed to be tubular adenoma with high-grade dysplasia limited to the mucosa. The patient is currently alive without any evidence of recurrence for six months after surgery. Although she had a past history of cervical cancer, the multiple tumors arising in the anal canal were unlikely to be related to human papilloma virus infection. Our case report underscores the importance of careful observations throughout colonoscopy to detect precancerous lesions, particularly in anatomically narrow segments.

Fig. 1

Immunohistochemical staining of p16 in cervical cancer (original magnification: 200 ×). Bar indicates 100 μm

Fig. 2

Findings of the first anal canal tumor. a Endoscopic appearance. b Histological appearance of a low magnification (original magnification: 20 ×). The border between adenoma and normal epithelium is indicated by a pair of arrowheads. Bar indicates 1 mm. The inset shows a higher-magnification view (original magnification: 200 ×)

Fig. 3

Findings of the second anal canal tumor. a Endoscopic appearance. b Histological appearance of a low magnification (original magnification: 40 ×). The border between adenoma and normal epithelium is indicated by an arrowhead. Bar indicates 1 mm. The inset shows a higher-magnification view (original magnification: 200 ×). c Immunohistochemical staining of p16 in the second anal canal tumor (original magnification: 200 ×). Only 4 % of tumor cells were positive for p16. Bar indicates 100 μm