Castleman disease (CD) is a rare chronic lymphoproliferative disease with unknown etiology and pathogenesis disease. When the lesion is located in the mediastinum, the diagnosis of CD is easy. However, if the lesion presents as a perigastric mass mimicking other subserosal gastric mesenchymal tumors, the diagnosis can be challenging. As few sonographic manifestations of hyaline-vascular variant CD, especially contrast-enhanced ultrasound (CEUS) imaging, as well as computed tomography (CT) and histopathological imaging, have been reported in literature, this case may provide a vivid example of a comprehensive CEUS and CT usage in the diagnosis and surgery with regard to CD. This report presents a case of a 50-year-old female diagnosed with hyaline-vascular variant CD in a random physical examination, the ultrasound examination first revealed a 24.3 mm × 15.4 mm hypoechogenic lesion abutting the stomach, esophagus, and liver, which was under the suspicion of gastrointestinal stromal tumor. Following a series of medical examinations, including CEUS, CT, postoperative histopathological examination, and immunohistochemical analysis, the patient was diagnosed with hyaline-vascular variant unicentric CD. After the mass was completely excised through laparoscopic surgery, the woman recovered very well without recurrence during a follow-up period of 15 months. Thus, mastering ultrasound and CT-imaging characteristics of CD and applying ultrasound and CT examination together would do help to preoperative diagnosis.