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E1196. Soft Tissue Sarcomas and Their Mimics in the Extremities: Imaging Features and Histopathological Correlation
Authors
  1. Musa Mufti; Department of Radiology, Stony Brook Medicine
  2. Beiyi Shen; Department of Radiology, Stony Brook Medicine
  3. Chad Downing; Department of Radiology, Mather Hospital; Department of Radiology, Stony Brook Medicine
  4. Jessa Tunacao; Department of Radiology, Mather Hospital; Department of Radiology, Stony Brook Medicine
  5. Elaine Gould; Department of Radiology, Stony Brook Medicine
  6. Kathleen Finzel; Department of Radiology, Stony Brook Medicine
  7. Daichi Hayashi; Department of Radiology, Stony Brook Medicine
Background
Soft tissue sarcomas are a rare heterogeneous group of cancers that account for almost 20% of pediatric and 1% of adult malignancies, about 20–40% of which occur in the torso [1]. According to the American Cancer Society, it is estimated about 13,130 new soft tissue sarcomas will be diagnosed and about 5,350 people are expected to die of soft tissue sarcomas in 2020 [2]. The most common types of sarcoma in adults are undifferentiated pleomorphic sarcoma (previously called malignant fibrous histiocytoma), liposarcoma and leiomyosarcoma. Liposarcoma and undifferentiated pleomorphic sarcomas are most common in legs [2]. Soft tissue tumors often cannot be distinguished on imaging as to benign or malignant, although the presence of restricted diffusion on diffusion weighted MRI sequence is a concerning feature for potential malignancy [3,4]. The purpose of this exhibit is to describe and illustrate imaging features of sarcomas in the extremities and their various subtypes as well as their mimics on imaging (primarily MRI) with pathological correlation.

Educational Goals / Teaching Points
1. To review epidemiological and clinical features of soft tissue sarcomas. 2. To describe and illustrate imaging characteristics of various types of soft tissue sarcomas in extremities and benign and malignant mimics of soft tissue sarcomas. 3. To highlight the need for multidisciplinary approach involving radiologists, pathologists, surgeons and oncologists to treat patients with soft tissue sarcoma in the extremities.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
1. Overview of extremity soft tissue sarcomas: Incidence, subtypes, and clinical presentation. 2. Pictorial review of MRI and other imaging characteristics of biopsy proven extremity sarcomas with pathologic correlation, including liposarcoma, myxofibrosarcoma, alveolar soft part sarcoma, high-grade fibrosarcoma, leiomyosarcoma, dermatofibrosarcoma, high-grade sarcoma, undifferentiated pleomorphic sarcomas, metastatic epithelioid sarcoma, and Kaposi sarcoma. 3. Pictorial review of general and imaging characteristics of mimics of sarcomas including benign (lipoma, hematoma, hemangioma, abscess, benign peripheral nerve sheath tumor, calcinosis cutis, nodular fasciitis, myositis ossificans, epidermal inclusion cyst, and intramuscular myxoma) and malignant lesions (malignant peripheral nerve sheath tumor, lymphoma and metastatic tumor). 4. Key issues for image-guided biopsy techniques specific to sarcomas. 5. Treatment options of soft tissue sarcoma.

Conclusion
Soft tissue sarcomas are rare and account for less than 1% of malignant tumors in adults. There are more than 50 subtypes. Location, pattern of growth, and MRI signal and enhancement characteristics may all raise suspicion for soft tissue sarcoma. Surgical planning relies heavily upon imaging findings and histology obtained via image-guided biopsy. Even though imaging characteristics are insufficient alone in differentiating between the numerous subtypes of sarcomas or even benign vs. malignant, MRI is a critical part of the assessment and may aid in distinguishing sarcomas from common mimics.