Polypoid gallbladder tumors with a deep hypoechoic area and a conically thickened outermost hyperechoic layer suggest shallow T2 carcinoma

Background Ultrasound findings of shallow T2 gallbladder carcinoma (GBC) with a favorable prognosis are not known. Purpose To confirm the criteria for ultrasound diagnosis of shallow T2 GBC. Material and Methods A detailed analysis of ultrasound and pathological correlation was conducted in two patients with pT1 GBC and seven with shallow pT2 GBC (subserosal-invasion depth <= 2 mm) at our institution from January 1988 to December 2017. Results A polypoid gallbladder tumor with a deep hypoechoic area represented a papillary adenocarcinoma invading the subserosa accompanied by abundant fibrosis and lymphocytic infiltration. Two cases of pT1 GBC did not present a deep hypoechoic area, whereas all seven cases of shallow pT2 GBC did. One case of pT1b GBC and four cases of pT2 GBC showed conical thickening of the outermost hyperechoic layer, whereas one case of pT1a GBC and three cases of pT2 GBC presented no change of the layer thickness. All shallow T2 GBCs showing a conically thickened outermost hyperechoic layer provided good postoperative prognoses. Conclusion Ultrasound images of shallow T2 GBC show a deep hypoechoic area with conical thickening or unchanging of an outermost hyperechoic layer. The former demonstrates pulling up the top of the layer at first and then thinning later as carcinoma invades with enlargement of the hypoechoic area, whereas the latter thinning of the layer from the beginning. Polypoid gallbladder tumors with a deep hypoechoic area and a conically thickened outermost hyperechoic layer suggest shallow T2 GBC and may provide good postoperative prognoses.