E1212. Sarcoma Mimics Versus Disguises: Recognizing Key Features to Avoid Misdiagnosis and Complications
  1. Brandon Sonnier; Baylor Scott and White Health
  2. Connie So; Baylor Scott and White Health
  3. Ricardo Garza-Gongora; Baylor Scott and White Health
Treatment of soft tissue sarcoma necessitates careful pre-operative planning. Conversely, unplanned biopsy or excision of an unexpected soft tissue sarcoma can cause a dilemma due to contamination of the surgical bed by tumor cells. An inadequate resection margin increases the risk of local sarcoma recurrence and often requires more extensive treatment after delayed referral to a specialized sarcoma surgeon. Therefore, this exhibit aims to increase awareness of potential imaging pitfalls and to guide the radiologist in navigating between examples of sarcoma mimics and sarcoma disguises.

Educational Goals / Teaching Points
First, this exhibit will review the Enneking classification of surgical margins, which is a popular classification used by orthopedic oncology surgeons when considering positive and negative tumor margins. Knowledge of the classification will aid the radiologist in providing relevant anatomical description on pre-operative imaging. Next, key features of various sarcoma mimics will be identified on different imaging modalities. Afterwards, key features of various sarcoma disguises will be identified on different imaging modalities.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
In this exhibit, sarcoma mimics refer to benign entities that may masquerade as malignancy, possibly due to an aggressive presentation or imaging appearance. Sarcoma disguises refer to soft tissue sarcomas that may appear benign initially, whether by clinical history of indolent growth or by unrecognized pitfalls of imaging. Key features of sarcoma mimics and disguises will be illustrated through ultrasound, CT, and MR. To begin with, sarcoma mimics will be organized into superficial and deep lesions. Superficial lesions include massive localized lymphedema, nodular fasciitis, fibromatosis, Morel-Lavallee lesion, and benign lipoma variants. Deep lesions occurring within or between muscles include elastofibroma dorsi, focal nodular myositis, diabetic myonecrosis, trauma (muscle tear pseudotumor), and infection. Subsequently, selected examples of indolent sarcomas potentially disguised as benign lesions will be discussed to include dermatofibrosarcoma protuberans, atypical lipomatous tumor (superficial well-differentiated liposarcoma), synovial sarcoma, and fibromyxoid sarcoma. Clinical presentation, image findings, and take home points of each case will be reviewed to increase awareness in the discerning radiologist.

Recognition of sarcoma mimics and disguises helps minimize unnecessary harm to a patient. Early guidance by the radiologist can facilitate appropriate referral and more efficient management before a tissue diagnosis is ultimately obtained. Relevant anatomical description on pre-operative imaging by the radiologist can also assist the surgeon in achieving negative tumor margins to improve prognosis and enhance survival of the patient.