Background <p>The initial diagnosis of dermatofibrosarcoma protuberans (DFSP) can be extremely challenging in the absence of confirmatory pathological examination combined with immunohistochemical staining. Clinically, DFSP most frequently arises in the trunk, extremities, and head and neck region, while mammary DFSP is exceptionally rare.</p> Case presentation <p>A 22-year-old female presented with a two-week history of a right breast mass. Bilateral breast ultrasound identified a hyperechoic mass within the subcutaneous fat layer of the right breast, with no definite space-occupying lesion observed in the mammary glandular tissue. Based on the imaging features, the mass was initially suspected to be a lipoma, and the patient subsequently underwent lumpectomy. However, Postoperative pathological examination revealed a spindle cell soft tissue tumor, which was subsequently confirmed as DFSP through immunohistochemistry and molecular studies. Following a multidisciplinary team (MDT) consultation involving breast surgery, pathology, medical oncology, and radiology, the patient underwent wide local excision.</p> Conclusion <p>We herein present a rare case of atypical breast DFSP with hyperechoic manifestations, which easily leads to diagnostic confusion with common benign breast lesions like lipoma. Accordingly, we emphasize a comprehensive diagnostic approach including clinical, imaging, and pathological evaluations is imperative for the accurate diagnosis of DFSP. However, the dual physical and psychological burden carried by young female patients should not be overlooked. It’s equally important to focus on their physical recovery and their emotional needs to optimize overall treatment outcomes.</p>