Undifferentiated Sarcoma




Malignant Fibrous Histiocytoma, High-Grade Pleomorphic Undifferentiated Sarcoma


CLINICAL SUMMARY


Undifferentiated sarcoma is the preferred term for the previously named malignant fibrous histiocytoma (MFH). This designation probably encompasses a common endpoint for poorly differentiated mesenchymal tumors rather than a specific pathologic entity. It is most common in the sixth and seventh decades and typically presents as a painless, enlarging soft tissue mass. Treatment includes wide surgical resection and radiation.


DIAGNOSTIC FEATURES


















History


  • Most common between 50 and 70 years of age



  • Painless, enlarging soft tissue mass

Location


  • Most commonly intramuscular but can occur in a subcutaneous location (5% to 10%)



  • Most common in the lower extremity: knee and thigh (45%), upper extremity (28%), trunk (17%), head and neck (10%)

MRI


  • Isointense with muscle on T1, high signal on T2



  • Large, high-grade tumors can demonstrate nonenhancing central regions representing necrosis




IMAGING




























  • A subcutaneous soft tissue sarcoma on the leg appears as a protuberant mass ( left ). Skin involvement often requires skin graft after excision.



  • Radiograph shows a protuberant subcutaneous mass without bone involvement ( right ).



  • Subcutaneous sarcomas are associated with better prognosis.










  • CT scan of a deep proximal adductor sarcoma shows a soft tissue mass ( arrow ) with density similar to that of muscle ( left ). The border of the tumor can appear indistinct on CT.



  • CT scan of a deep medial thigh sarcoma demonstrates large, central, hypodense necrosis and thick nodular walls, representing viable tumor ( right ).


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