Villous Adenoma of the Sigmoid Colon

Villous adenoma of the colon is a somewhat rare benign tumor which has remained unmentioned in the radiological literature. Such a lesion was recently studied in our department and we believe that the history and the unusual roentgenologic manifestations may well be characteristic of this interesting neoplasm. Incidence: These tumors are encountered largely in the later decades, the average age of incidence being in the midfifties, with no apparent familial or sexual tendency. They occur singly and have been stated to constitute from 0.1 to 6.6 per cent of all rectal and sigmoid lesions (10). In one series of 1,144 tumors of the colon and rectum, villous adenomas were said to represent 2.3 per cent of the total (2). Pathology: The term “villous tumor” was originated by Holmes, a British pathologist, in 1860. At various times, and by various authors, these neoplasms have been called papillomas, mucous or columnar papillomas, villous papillomas, papillary polyps or adenomas, villous adenomas, and villomas. The usual site of occurrence is in the colon, primarily in the rectum and sigmoid, where approximately 80 per cent of the tumors are found (13). Similar lesions have been described in the stomach and gallbladder. The benign epithelial tumors of the colonic mucosa have been divided into two categories, the villous adenoma and the adenomatous polyp. The adenomatous polyp is typically a compact, spheroid, pedunculated mass; the villous adenoma is a soft, sessile tumor without a pedicle. The adenomatous polyp is said to occur in about 7 per cent of all adults, while the villous adenoma is relatively rare. Grossly the villous adenoma ranges in size from a nodule several centimeters in diameter to a mass of enormous size, completely encircling the bowel. The tumor is spongy, red or red-gray in color, and usually sessile, with a broad flat base. It is extremely soft and velvety and is made up of a large number of friable villi or finger-like projections joined at their bases in a pattern which is frequently lobulated. The entire lesion is usually covered by thick, viscid mucus. Occasionally the tumor appears pedunculated; this is felt to be due to stretching of the redundant surrounding mucosa by the weight of the mass. Microscopically the surface is made up of multiple tiny villi covered by a layer of columnar cells in a close, almost normal, relationship with the muscularis mucosa. The connective tissue of the submucosa is edematous and highly vascular. In typically benign lesions there is no involvement of the deeper layers. However, there is said to be a strong tendency toward invasion and malignant transformation. Symptoms: The most prominent and characteristic symptom is the profuse discharge of large amounts of mucus produced by the tumor.