Case report: Hypoechoic area as an ultrasound finding suggesting subserosal invasion in polypoid carcinoma of the gall bladder

Ultrasound studies have demonstrated the gall bladder wall to consist of two or more (usually three) layers. Gall bladder tumours with neither a thinned nor split outermost hyperechoic layer are confined to the mucosa or muscle layer, or have only invaded the shallow subserosa. Differentiation of these two types of tumour has posed difficulties. We report a case of polypoid gall bladder carcinoma invading the shallow subserosa with a thickened outermost hyperechoic layer but a hypoechoic area in the deeper part of the tumour. Ultrasound and pathological correlation in this case demonstrated that the hypoechoic area represented an adenocarcinoma invading the subserosa accompanied by abundant fibrosis.