Squamous Metaplasia in Tubular Adenoma of Sigmoid Colon: A case report

ABSTRACT

The occurrence of squamous metaplasia(morule) in colorectal mucosa and adenocarcinoma, althrough rare, has been well documented. In contrast, very little mention has been given to mature squamous cells seen in colorectal polyps or adenomas. A 42-year-old woman presented with a 2-month history of diarrhea and melena. Proctosigmoidoscopy revealed a 4 cm-sized polypoid tumor 20 cm above the anal verge. Colonoscopic biopsy showed tubular adenoma, and a segmental resection of sigmoid colon was done. Microscopically, the tumor was c classical tubular adenoma containing multiple solid nests of squamous cells scattered only in the neoplasm; the squamous nests were generally small, and some showed direct continuity with adenomatous glands. The squamous cells were keratinizing and had regular nuclei with no mitotic activity. The importance of this phenomenon lies in its pathologic recognition, and the findings suggest that awareness of this rare occurrence in colorectal polyps should avert such overdiagnosis, and consequently prevents unnecessary radical surgery.