Contrast-enhanced ultrasound imaging characteristics of malignant transformation of a localized type gallbladder adenomyomatosis: A case report and literature review.

Gallbladder adenomyomatosis (GAM) is an acquired, reactive, tumor-like condition. Malignant transformation is extremely rare, and imaging features during contrast-enhanced ultrasound (CEUS) have not been described before. Herein, we describe a 73-year-old Asian man who had been diagnosed with gallbladder carcinoma by conventional ultrasonography (US). Based on additional radiological findings, we believed that it was a localized adenomyomatosis. However, the histopathological diagnosis was adenocarcinoma originate from adenomyomatosis with serosal invasion. We believe this is the first case of adenocarcinoma derived from GAM with characteristics of CEUS findings. This case is presented to indicate a clinical awareness of malignant transformation of GAM and discuss the radiology significance with an emphasis on CEUS.