A 70-year old man was admitted for investigation of muscular weakness and the passage of large amounts of mucus per rectum. The patient was found to be hypokalaemic. A tumour of sigmoid colon was discovered and later resected.
A 15 cm long segment of colon has been opened longitudinally to display a large sessile tumour with a velvety surface. The tumour measures 11 x 7 cm. in diameter and approaches to within 2 cm of the distal resection margin. The mucosa is otherwise normal. The serosal surface is unremarkable. Histological examination confirmed the presence of a villous adenoma.
Villous adenomas occasionally secrete large amounts of mucoid protein and/or potassium rich fluid, sufficient to result in hypoalbuminaemia or hypokalaemia. Villous adenoma is the least common but most ominous type of adenomatous polyp. Invasive carcinoma is present in up to 30% of cases at the time of resection.