E1993. A Review of Intra-Abdominal Soft Tissue Sarcoma for the Abdominal Imager and Interventionalist: Imaging and Clinical Management
  1. Edwarda Golden; Johns Hopkins Hospital
  2. Ihab Kamel; Johns Hopkins Hospital
Soft tissue sarcomas are a heterogeneous group of mesenchymal malignancies, comprising 1% of adult malignancies. Intra-abdominal sarcomas include liposarcoma (LPS), leiomyosarcoma (LMS), gastrointestinal stromal tumors (GIST), and other rarer sarcomas. The focus of this exhibit will be on two of the most common, LPS and LMS, and how they differ from other abdominal sarcomas and from sarcomas that occur elsewhere in the body.

Educational Goals / Teaching Points
After reviewing this exhibit, the viewer will be familiar with the epidemiology, imaging appearance, staging, management, and surveillance of abdominal LPS and LMS.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
LPS is the most common retroperitoneal sarcoma and there are 4 subtypes: well-differentiated (WD), dedifferentiated (DD), myxoid, and pleomorphic. WD-LPS, also known as atypical lipomatous tumor (ALT) when occurring in the extremities, is low-grade and does not metastasize. It appears as a well-defined mass with fat attenuation on CT and with similar signal characteristics to subcutaneous fat on MR. DD-LPS can arise from existing WD-LPS or de-novo. It appears as a heterogeneous soft tissue mass on imaging and may not demonstrate areas of fat density. DD-LPS can metastasize. Myxoid LPS is rare in the retroperitoneum, usually arising in the thigh, but can metastasize intraabdominally. Pleomorphic LPS is the highest grade and presents as a heterogeneous soft tissue mass. LMS are sarcomas that arise from cells that have undergone smooth muscle differentiation. They arise from anywhere with smooth muscle, including vessels and bowel. On imaging they appear as soft tissue masses and do not have specific imaging characteristics. LMS occurring in venous structures can present as both intraluminal and extraluminal masses. Venous LMS can obstruct and present with findings of venous congestion. Radiologists play a key role in the work up of these tumors. Imaging is used to determine the feasibility of total resection and to evaluate for metastases. Furthermore, given the often-nonspecific appearance of these masses, preoperative image-guided tissue sampling is frequently necessary. The risk of needle track seeding is negligible with coaxial sheathed biopsy needles, which limit the number of times the pseudocapsule of the tumor is breached and limit contact of the needle with adjacent tissues during removal. Good biopsy technique is essential for providing a histopathologic diagnosis, prognostic information, and sufficient tissue for genetic testing. Intra-abdominal sarcoma is treated much like sarcomas elsewhere - with wide excision. Radiation therapy is also a mainstay of treatment. Currently, chemotherapy does not play a large role in sarcoma management. Unfortunately, total resection is sometimes not possible due to tumor location, and even if resected, low-grade sarcomas often recur. Due to this high recurrence rate, patients are followed closely with imaging.

Abdominal radiologists play a key role in the diagnosis and management of abdominal sarcoma. Understanding the imaging findings and clinical perspective guiding management helps to better serve patient care.