Pelvic Soft Tissue Sarcoma MRI

Soft tissue sarcoma is a type of cancer that begins in the soft tissues of the body, which include muscles, tendons, fat, blood vessels, lymph vessels, nerves, and tissues around joints. These tumors can occur anywhere in the body but are most commonly found in the arms, legs, and abdomen.


The exact cause of soft tissue sarcoma is not well understood, but several risk factors have been identified:

  • Genetic Factors: Certain inherited syndromes, such as Li-Fraumeni syndrome, neurofibromatosis type 1, and familial adenomatous polyposis, increase the risk.
  • Radiation Exposure: Previous radiation therapy for other cancers can increase the risk of developing soft tissue sarcomas.
  • Chemical Exposure: Exposure to certain chemicals, such as vinyl chloride, arsenic, and dioxins, has been linked to a higher risk.
  • Chronic Lymphedema: Long-term swelling in the limbs, often due to damage to the lymphatic system, can lead to angiosarcoma, a type of soft tissue sarcoma.


The symptoms of soft tissue sarcoma can vary depending on the location and size of the tumor. Common symptoms include:

  • Lump or Swelling: The most common symptom is a painless lump or swelling in the soft tissues of the body.
  • Pain: As the tumor grows, it may press against nerves and muscles, causing pain or discomfort.
  • Limited Range of Motion: If the tumor is near a joint, it may cause stiffness or limit the range of motion.
  • Other Symptoms: Depending on the tumor’s location, other symptoms may include abdominal pain, blood in stool or vomit, and difficulty breathing.


Diagnosis of soft tissue sarcoma typically involves several steps:

  • Medical History and Physical Exam: The doctor will review the patient’s medical history and conduct a physical examination.
  • Imaging Tests: These may include X-rays, CT scans, MRI scans, and PET scans to visualize the tumor and determine its size and extent.
  • Biopsy: A biopsy involves taking a small sample of the tumor tissue for laboratory analysis to confirm the diagnosis and determine the type of sarcoma.


Treatment for soft tissue sarcoma depends on various factors, including the type, size, location, and stage of the tumor, as well as the patient’s overall health. Common treatment options include:

  • Surgery: The primary treatment for soft tissue sarcoma is the surgical removal of the tumor, often with a margin of healthy tissue to ensure complete removal.
  • Radiation Therapy: High-energy beams are used to kill cancer cells or shrink tumors before surgery (neoadjuvant) or after surgery (adjuvant) to eliminate any remaining cancer cells.
  • Chemotherapy: Drugs are used to kill cancer cells, often used for certain types of soft tissue sarcomas or in cases where the cancer has spread (metastasized).
  • Targeted Therapy: These drugs target specific molecules involved in the growth and spread of cancer cells and are used for specific types of sarcomas with known molecular targets.
  • Immunotherapy: This treatment helps the body’s immune system recognize and attack cancer cells and may be used for certain types of sarcoma.

MRI Appearance of Soft Tissue Sarcoma

MRI T1 Appearance of Soft Tissue Sarcoma

On T1-weighted MRI images, soft tissue sarcomas typically appear as iso- to hypointense relative to normal muscle tissue. The tumor may demonstrate heterogeneous signal intensity due to the presence of different tissue components, such as hemorrhage, necrosis, or fat. This sequence is particularly useful for defining the anatomical location and extent of the tumor, as well as its relationship to adjacent structures. T1 images can help identify any infiltration into nearby fat planes and muscular compartments, providing a clear delineation of the tumor margins.

MRI T2 Appearance of Soft Tissue Sarcoma

T2-weighted MRI images usually show soft tissue sarcomas as hyperintense relative to normal muscle tissue. This increased signal intensity is due to the high water content within the tumor, reflecting edema and necrosis. T2-weighted images are valuable for assessing the internal architecture of the sarcoma, often revealing areas of cystic degeneration or hemorrhage. The heterogeneity seen on T2 images can help in characterizing the tumor and differentiating it from benign soft tissue masses, which typically appear more homogeneous.

MRI STIR Appearance of Soft Tissue Sarcoma

On Short Tau Inversion Recovery (STIR) sequences, soft tissue sarcomas typically appear hyperintense due to the suppression of fat signals and the prominence of fluid signals. STIR is particularly sensitive to edema and helps in detecting the extent of tumor infiltration, especially in the presence of surrounding soft tissue edema. This sequence is crucial for identifying tumor margins and any peritumoral edema, which can assist in surgical planning and assessing the response to treatment.

MRI T1 Fat-Saturated Post-Contrast Appearance of Soft Tissue Sarcoma

T1 fat-saturated post-contrast images of soft tissue sarcomas often show marked enhancement of the tumor due to the increased vascularity and permeability of the sarcoma tissue. This enhancement pattern can be heterogeneous, reflecting areas of viable tumor, necrosis, and fibrosis. The use of fat saturation helps to suppress the background fat signal, thereby enhancing the visibility of the contrast uptake within the tumor. This sequence is essential for assessing the tumor’s vascular supply and delineating viable tumor tissue from necrotic areas.

MRI DWI (b0, b1000) and ADC Appearance of Soft Tissue Sarcoma

Diffusion-weighted imaging (DWI) at b0 and b1000 values provides additional characterization of soft tissue sarcomas. On DWI, these tumors typically show high signal intensity due to restricted diffusion, reflecting the densely cellular nature of the tumor. The Apparent Diffusion Coefficient (ADC) map usually shows low values within the tumor, corresponding to the areas of restricted diffusion seen on high b-value DWI images. These findings are helpful in differentiating malignant tumors from benign lesions, which generally exhibit less restricted diffusion and higher ADC values. DWI and ADC maps are also valuable for monitoring treatment response, as changes in diffusion characteristics can indicate tumor necrosis or viability.

T2 TSE sagittal image shows Soft Tissue Sarcoma

T2 TSE sagittal image shows Soft Tissue Sarcoma
T2 TSE sagittal image shows Soft Tissue Sarcoma11

STIR coronal image shows Soft Tissue Sarcoma

STIR coronal image shows Soft Tissue Sarcoma 1
STIR coronal image shows Soft Tissue SarcomaSTIR coronal image shows Soft Tissue Sarcoma 3

T1 coronal image shows Soft Tissue Sarcoma

T1 coronal image shows Soft Tissue Sarcoma 1
T1 coronal image shows Soft Tissue Sarcoma 2

STIR axial image shows Soft Tissue Sarcoma

STIR axial image shows Soft Tissue Sarcoma 3
STIR axial image shows Soft Tissue Sarcoma 3

T1 axial image shows Soft Tissue Sarcoma


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