What imaging modality is recommended for a large, firm, and growing mass on the upper back, previously reported as a fatty tumor by a general surgeon (General Surgeon), with indistinct edges and significant size?

Imaging Recommendation for Large, Firm, Growing Upper Back Mass

MRI is the recommended first-line imaging modality for evaluating this large, firm, growing mass on the left upper back near the neck/shoulder that was previously reported as fatty but has concerning features.1, 2

Rationale for MRI as Primary Imaging

• MRI provides superior soft tissue contrast resolution and multiplanar imaging capability, making it the imaging modality of choice for evaluating concerning soft tissue masses, especially those that are large, firm, and growing 1, 2
• MRI can effectively characterize the mass, determine its relationship to adjacent structures, and provide crucial information for local staging 2
• MRI is particularly valuable for masses with indistinct edges, as it can delineate the extent of the lesion and its relationship to surrounding tissues 1, 3
• The concerning features of this mass (large size, firm consistency, growth, and indistinct edges) warrant comprehensive evaluation with MRI rather than less definitive imaging modalities 1, 2

Alternative Initial Approach

• If MRI is not immediately available, ultrasound could be considered as an initial triage tool to determine if the mass has typical benign features or concerning characteristics 1
• Ultrasound can help differentiate solid from cystic lesions and provide information about vascularity 1, 4
• However, ultrasound has limitations for large, deep masses and those with complex anatomical relationships 1

Radiographs

• Radiographs should be obtained as a complementary study but not as the sole imaging modality 1, 5
• Radiographs can identify calcifications, bone involvement, or intrinsic fat in some cases, but have limited sensitivity for soft tissue masses 1, 4
• The diagnostic yield of radiographs for soft tissue masses is approximately 62%, with identification of calcification in 27%, bone involvement in 22%, and intrinsic fat in only 11% of cases 1, 4

Clinical Considerations

• The mass has several concerning features that raise suspicion for potential malignancy:
  • Large size (approximately half a baseball)
  • Firm consistency despite previous characterization as fatty
  • Progressive growth
  • Indistinct edges 1, 6
• Any soft tissue mass that is increasing in size, larger than 5 cm, deep-seated, or painful should prompt thorough evaluation 1
• Physical examination alone is insufficient, as it correctly identifies only about 85% of soft tissue tumors 4, 2

Next Steps After Imaging

• If MRI findings suggest a potentially malignant lesion, referral to a specialized sarcoma center with a multidisciplinary team is recommended 1, 2
• Tissue sampling (core needle biopsy) should be performed after MRI to guide appropriate management 2
• For masses with benign imaging characteristics but concerning clinical features, surgical excision may still be warranted 4

Common Pitfalls to Avoid

• Relying solely on physical examination or previous clinical assessment without appropriate imaging 4, 2
• Proceeding directly to biopsy without MRI, which can lead to sampling error and inadequate surgical planning 2
• Assuming a mass is benign based on a previous assessment when clinical features suggest otherwise 6, 7
• Delaying evaluation of a growing mass with concerning features 1, 6