Cholesterol polyp of the gallbladder showing rapid growth and atypical changes--a case report.

We report on a case of resected cholesterol polyp with typical ultrasonic findings that became atypical, with a 40% increase in diameter, over a period of about 10 months. The resected specimen revealed a black polyp with a large-nodular appearance. The pathological diagnosis was cholesterol polyp with marked glandular proliferation, and the glandular cavity showed cystic dilatations filled with dark brown fluid. It is suspected that the aggregation of large numbers of these dilated glands explained the black color, the rapid growth, and the development leading to the atypical ultrasonic findings.