Abstract: A 43-year-old female patient was admitted to the hospital due to a gradually enlarging scalp mass in the parieto-occipital region found over the past six months. Physical examination revealed a protuberant mass on the occipital scalp with medium to firm texture, reddish overlying skin and sparse local hair. Preoperative ultrasonography showed a solid hypoechoic nodule under the scalp with relatively clear boundaries and heterogeneous internal echo, with abundant and disordered blood flow visible inside and around the lesion,.which was preoperatively diagnosed as hemangioma. Postoperative pathological examination confirmed proliferating trichilemmal tumor with prominent foreign body granulomatous reaction. Combined with relevant literature, this paper analyzes the ultrasonographic features and causes of misdiagnosis of this disease,and suggests that proliferating trichilemmal tumor should be included in the differential diagnosis of hypervascular scalp nodules in clinical practice.

Key words: scalp mass, proliferating trichilemmal tumor, ultrasonography, hemangioma