BackgroundDermatofibrosarcoma protuberans is extremely rare in children, making a correct diagnosis by clinicians is usually difficult due to its nonspecific manifestations, the recurrence of dermatofibrosarcoma protuberans after resection has always been a perplexing problem for clinicians. Ultrasound plays an irreplaceable role in the assessment of dermatofibrosarcoma protuberans, although there is a limitation in the diagnosis of the tumor.Case ReportA 10‐year‐old boy led by his parents sought for surgical treatment because of the growing mass. Physical examination and preoperative ultrasonography showed that the mass was clear, and the routine resection of mass was performed. Six days postoperatively, histopathological examination indicated that the mass was dermatofibrosarcoma protuberans, and the peripheral and deep resection margins were positive. The patient was informed that a second extended resection was required. The second postoperative pathology showed a negative margin, and the patient was discharged. Postoperative follow‐up was assessed by ultrasound examination, and the patient had no abnormalities.ConclusionsDermatofibrosarcoma protuberans should be included in the differential diagnosis when the wide base subcutaneous lesion has suspicious features with high vascularity on ultrasound. If an ultrasound reveals a mass with abundant blood flow, clinicians should routinely perform the extended resection. Wide surgical excision may reduce the risk of reoperation and recurrence, and long‐term follow‐up is necessary to evaluate postoperative outcomes.