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2334. Imaging Features of Musculoskeletal Leiomyosarcoma with Pathologic Correlation
Authors * Denotes Presenting Author
  1. Jon Olson *; American Institute for Radiologic Pathology; Walter Reed National Military Medical Center
  2. Mark Murphey; American Institute for Radiologic Pathology; Walter Reed National Military Medical Center
  3. Mark Kransdorf; Mayo Clinic Scottsdale
  4. James Jelinek; Medstar Washington Hospital Center
  5. Alejandro Luiña Contreras; Joint Pathology Center
Objective:
To describe the radiologic appearance of musculoskeletal leiomyosarcoma with pathologic correlation.

Materials and Methods:
We retrospectively reviewed 15 pathologically confirmed cases of leiomyosarcoma. Radiologic studies were reviewed by three (3) musculoskeletal radiologists with agreement by consensus and included radiographs (n=5), CT (n=5), MRI (n=10) and US (n=2). Evaluation included patient demographics, lesion location and size, presence and character of calcification, evidence of hemorrhage, central necrosis, neurovascular encasement and intrinsic characteristics on CT and MRI.

Results:
Patient ages ranged from 34 - 86 years with an average age of 64 years. There was an equal distribution between men and women. Presenting symptoms were a painless mass (66%) which was slowly increasing in (75%). The lesions were equally distributed between subcutaneous (33%), intermuscular (33%) and intramuscular (33%) locations and most frequently in the thigh (65%) and lower leg (15%), followed by the forearm (5%), upper arm (5%), hand (5%), and ribs (5%). Tumors were typically larger than 5cm at presentation (80%) with an average lesion size was 12 x 10 x 7 cm. On US, the tumors were well defined with moderate hypoechogenicity. Doppler interrogation showed mild hypervascularity and confirmed neurovascular encasement. Radiographs demonstrate a soft tissue mass with amorphous, internal calcification in 20% of cases. On CT, all tumors were well-defined masses hypodense to adjacent muscle. Following contrast administration, tumors demonstrated moderately heterogeneous peripheral nodular and thick septal enhancement. There was no evidence of cortical destruction or medullary invasion. On MRI, all tumors were well defined (100%) and isointense to muscle with T1 weighting, with mild (50%) to moderate (50%) heterogeneity. On T2 or fluid weighted images, the tumors demonstrated variable signal intensity with predominantly hyperintense signal (50%) of cases, and intermediate (25%) and hypointense (25%) signal with moderate (50%) to marked (50%) heterogeneity. Post contrast imaging demonstrates moderate diffuse (50%) or peripheral nodular and thick septal (50%) enhancement. Hemorrhage was apparent in 50% of tumors although all showed central necrosis. Neurovascular encasement and mild surrounding edema were noted in 75% of cases, including multiple tumors which appear to arise from and obliterate the encased venous structures.

Conclusion:
Leiomyosarcomas in our series demonstrate a nonspecific imaging appearance of a well-defined, heterogeneous, soft tissue mass which typically demonstrates neurovascular encasement (75%), central necrosis (75%) and hemorrhage (50%). A subset of these tumors is intimately associated with the neurovascular bundle and appear to arise from and obliterate the encased vein, which are more specific findings suggestive of the diagnosis. The size at presentation is typically larger than 5cm in a subcutaneous, intermuscular or intramuscular location, most commonly in the thigh or lower leg.