In a 62-year-old man with a rapidly enlarging painless 5 cm soft‑tissue mass of the lower thigh showing calcifications and bone involvement on plain radiograph, what is the most appropriate next step in management?

MRI with Contrast is the Most Appropriate Next Step

In this 62-year-old man with a rapidly growing 5 cm soft tissue mass showing calcifications and bone involvement on plain radiograph, MRI with contrast should be obtained urgently before any biopsy or surgical intervention. 1, 2

Rationale for MRI as the Next Step

MRI has become the technique of choice for detecting and characterizing soft tissue masses, providing superior soft-tissue contrast, multiple-image plane capabilities, and critical information for lesion conspicuity, intrinsic characterization, and local staging. 1 This is particularly essential when plain radiographs have already demonstrated concerning features such as calcifications and bone involvement—findings present in 27% and 22% of proven soft tissue masses respectively, and often associated with malignancy. 1, 3

Why MRI Takes Priority Over Biopsy

• A fundamental tenet of orthopedic oncology states that if a practitioner or institution is not equipped to perform accurate diagnostic studies or definitive treatment, the patient should be referred to a treatment center BEFORE performance of biopsy. 1 This patient requires comprehensive staging imaging before tissue diagnosis to optimize surgical planning and avoid compromising future treatment options. 2

• The biopsy must be planned by a specialist sarcoma multidisciplinary team so that the biopsy tract can be safely removed during definitive surgery. 2 Performing a biopsy without proper imaging and surgical planning can seed tumor cells along the biopsy tract and complicate definitive resection, directly impacting morbidity and mortality. 1

• MRI provides the most accurate information for diagnosis and surgical/radiotherapy planning for extremity soft tissue tumors, allowing assessment of neurovascular involvement, compartmental anatomy, and relationship to bone—all critical for determining resectability and surgical approach. 1, 2

Clinical Features Demanding Urgent Advanced Imaging

This patient's presentation contains multiple red flags requiring immediate specialist evaluation:

• Rapidly growing mass (concerning for malignancy) 2, 4
• Size >5 cm (meeting criteria for urgent specialist referral) 1, 5
• Calcifications on radiograph (present in 27% of soft tissue masses, can indicate sarcoma) 1, 3
• Bone involvement (present in 22% of soft tissue masses, highly concerning for malignancy or aggressive process) 1, 3
• Deep location in thigh (higher risk than superficial lesions) 1, 5

Why Other Options Are Inappropriate at This Stage

CT scan alone is insufficient because while CT is useful for characterizing mineralization patterns and assessing cortical bone involvement, it lacks the soft-tissue contrast resolution necessary for optimal surgical planning and cannot adequately assess neurovascular structures without contrast administration. 1 CT is most appropriate when MRI is contraindicated or as an adjunct to MRI, not as the primary staging modality. 1

PET scan is not typically ordered for initial evaluation of a soft tissue mass and should not precede MRI. 1 While PET-CT may be considered before radical surgery in select cases, it is not yet proven as a routine investigation and does not provide the anatomic detail necessary for surgical planning. 2

Punch biopsy is completely inappropriate for a deep 5 cm mass with bone involvement, as it would provide inadequate tissue for diagnosis and could compromise subsequent treatment. 1, 2 Core needle biopsy (not punch biopsy) is the standard approach, but only after proper imaging and multidisciplinary planning. 1, 2

Excisional biopsy/mass excision without proper staging is a critical error that can result in inadequate margins, tumor spillage, and the need for more extensive re-resection with worse functional outcomes and potentially compromised survival. 1 Excisional biopsy is only appropriate for superficial lesions <5 cm, which this case clearly is not. 1

Immediate Management Algorithm

1. Order MRI with contrast of the affected thigh urgently 1, 2
2. Simultaneously refer to a specialist sarcoma multidisciplinary team (this patient meets criteria: deep mass, >5 cm, bone involvement, rapid growth) 1, 5, 2
3. Obtain CT chest for staging (to exclude pulmonary metastases, as soft tissue sarcomas predominantly metastasize to lungs) 2
4. Consider CT abdomen/pelvis for high-grade lower extremity sarcomas 2
5. Await multidisciplinary team review before any biopsy to ensure proper biopsy planning and tract placement 1, 2

Critical Pitfalls to Avoid

• Never perform biopsy before obtaining MRI and specialist consultation—this can compromise surgical margins and worsen outcomes. 1
• Do not assume calcification indicates a benign process—many sarcomas (including synovial sarcoma, extraskeletal osteosarcoma, and soft tissue chondrosarcoma) can calcify. 3, 6
• Bone involvement on radiograph is a red flag requiring immediate specialist referral—this suggests either aggressive soft tissue sarcoma with bone invasion or primary bone malignancy with soft tissue extension. 2, 3
• Rapid growth in a painless mass is particularly concerning—the most common presentation of sarcoma is a painless enlarging soft tissue mass, and rapid growth increases malignancy risk. 2, 4

This patient requires urgent MRI followed by specialist sarcoma team evaluation to optimize survival and functional outcomes through proper surgical planning and coordinated multimodality treatment. 1, 2