Management of 4.6 cm Soft Tissue Mass Inferior to Glenohumeral Joint
MRI of the shoulder without IV contrast is the next step to characterize this 4.6 cm soft tissue mass and determine whether it represents a benign lesion (lipoma, cyst), an aggressive sarcoma, or another pathology requiring urgent specialist referral. 1, 2
Immediate Diagnostic Pathway
Why MRI Without Contrast is Indicated
- MRI provides the most accurate information for diagnosis and surgical/radiotherapy planning for soft-tissue tumors affecting the extremity, trunk, and pelvis. 1
- The American College of Radiology recommends MRI without IV contrast as the appropriate imaging study for evaluating soft tissue pathology in the shoulder region. 2
- MRI can characterize the mass as fat density (lipoma), cystic, vascular, or solid/aggressive, which directly impacts management decisions. 1
- MRI has 90% specificity and accuracy for distinguishing benign from malignant soft tissue masses, with a 94% negative predictive value for malignancy. 3
Critical Size and Location Considerations
- This 4.6 cm mass meets criteria for urgent evaluation, as masses >5 cm, deep-seated location, or increasing size warrant direct referral to specialist sarcoma services. 1
- The inferior glenohumeral location makes this a deep-seated mass requiring comprehensive characterization before any intervention. 1
- While most soft tissue masses in primary care are benign lipomas, atypical lipomatous tumors (well-differentiated liposarcomas) tend to be larger, deep-seated, and in the lower limb—but can occur in the shoulder region. 1
What MRI Must Determine
The MRI evaluation should specifically assess:
- Signal characteristics on T1 and T2 sequences to identify fat content (bright on T1), fluid/cystic nature (bright on T2), or solid tissue components. 3, 4, 5
- Lesion margins (well-defined vs infiltrative), signal homogeneity, and any neurovascular or bone involvement—features that help distinguish benign from malignant pathology. 3, 4
- Relationship to rotator cuff, neurovascular structures, and bone to guide surgical planning if intervention is needed. 1, 2
Post-MRI Decision Algorithm
If MRI Suggests Benign Lipoma or Simple Cyst
- Reassurance and clinical follow-up may be appropriate if imaging features are definitively benign. 1
- However, any uncertainty on MRI requires tissue diagnosis via percutaneous core needle biopsy under image guidance. 1
If MRI is Indeterminate or Suggests Malignancy
- Immediate referral to a specialist sarcoma multidisciplinary team (MDT) before any surgical intervention or biopsy. 1
- Percutaneous core needle biopsy (multiple cores) should be performed by the specialist team, with the biopsy tract planned for excision during definitive surgery. 1
- The biopsy should be reviewed by a specialist sarcoma pathologist, as discrepancy rates between non-specialist and specialist pathology review range from 8-35%. 1
If Sarcoma is Confirmed
- CT chest for staging to exclude pulmonary metastases prior to definitive treatment. 1
- All treatment decisions (surgery, chemotherapy, radiotherapy timing) must be made by the sarcoma MDT. 1
- Complete surgical excision with a margin of normal tissue is the standard treatment for localized soft tissue sarcomas. 1
Critical Pitfalls to Avoid
- Never perform excisional biopsy or surgical removal outside a specialist sarcoma center, as this compromises oncologic outcomes and increases local recurrence risk. 1
- Do not assume a "benign-appearing" mass on MRI is truly benign unless the tumor can be specifically named with well-established MRI features (e.g., classic lipoma with homogeneous fat signal). 4
- When uncertainty exists, characterize the mass as indeterminate and approach as a potential sarcoma until proven otherwise. 4
- The risk of biopsy tract seeding is very small, but proper planning ensures the tract can be excised during definitive surgery. 1