What is the next step in management for a 35-year-old man with a 6‑month left axillary soft‑tissue swelling, ultrasound showing a 3.2 × 1.9 × 2.0 cm hypoechoic lesion with irregular margins, an adjacent axillary lymph node with 0.4 cm cortical thickening, and a 1.3 × 0.7 × 0.8 cm calcific focus inferior to the lesion?

Management of Left Axillary Soft Tissue Mass with Suspicious Features

This patient requires urgent referral to a specialist sarcoma multidisciplinary team (MDT) within 2 weeks and should undergo MRI with contrast of the affected region before any biopsy is performed. 1, 2

Critical Red Flags Present

This presentation contains multiple concerning features that mandate specialist evaluation:

• Deep soft tissue mass measuring 3.2 cm meets size criteria for urgent cancer pathway referral 1
• Irregular borders on ultrasound are highly suspicious for malignancy and contraindicate simple observation 1, 2
• Adjacent lymph node with cortical thickening (0.4 cm) suggests potential nodal involvement, which occurs in certain sarcoma subtypes including synovial sarcoma and epithelioid sarcoma 1, 2
• Calcific focus inferior to the lesion is present in approximately 27% of proven soft tissue masses and can be a marker of sarcoma 1, 2
• Six-month duration with persistent swelling indicates a progressive process requiring definitive diagnosis 1

Immediate Next Steps

1. Urgent MRI with Contrast (Before Biopsy)

MRI with contrast is the mandatory next imaging study and must be obtained before any tissue sampling. 1, 2

• MRI provides superior soft tissue contrast resolution and multiplanar capability essential for characterizing the lesion, assessing neurovascular involvement, and planning surgical approach 1, 2
• MRI is the technique of choice for detecting and characterizing soft tissue masses in the axilla, offering the most accurate assessment of compartment anatomy and relationship to critical structures 2
• Performing a biopsy before MRI can seed tumor cells along the tract, compromise surgical margins, and worsen functional and survival outcomes 2

2. Specialist Sarcoma MDT Referral

Refer immediately via suspected cancer pathway for appointment within 2 weeks. 1

• All patients with ultrasound findings suggestive of soft tissue sarcoma (irregular borders, deep location, adjacent lymph node involvement) require specialist MDT management 1
• The MDT should include pathologists, radiologists, surgeons, radiation therapists, and medical oncologists with sarcoma expertise 1
• Decisions about biopsy technique, timing, and tract placement must be made by the sarcoma MDT to ensure the biopsy tract can be safely removed during definitive surgery 1, 2

3. Staging Investigations

CT chest should be performed to exclude pulmonary metastases, as soft tissue sarcomas have a predominant pattern of lung metastases 1, 2

Additional staging considerations based on final histology:

• Regional lymph node assessment by ultrasound or cross-sectional imaging is particularly important given the cortical thickening already identified, especially if synovial sarcoma, clear cell sarcoma, angiosarcoma, or epithelioid sarcoma is suspected 1, 2
• PET-CT may be considered before radical surgery in selected cases, though it is not yet proven as routine investigation 1

Biopsy Planning (Only After MRI and MDT Review)

Percutaneous core needle biopsy is the standard approach once imaging is complete and MDT planning has occurred. 1, 2

• Multiple cores should be taken under image guidance to maximize diagnostic yield 1
• The biopsy tract must be planned so it can be excised en-bloc with the definitive resection 2
• Fine needle aspiration is not recommended as a primary diagnostic modality 1

Critical Pitfalls to Avoid

• Never perform excisional biopsy or any tissue sampling before MRI and specialist consultation - this can lead to inadequate margins, tumor spillage, and need for more extensive re-resection, adversely affecting functional outcome and survival 2
• Do not rely on ultrasound characteristics alone to exclude malignancy - while ultrasound has high sensitivity (94.1%) and specificity (99.7%) for superficial masses, irregular borders and deep location require definitive cross-sectional imaging 1
• Do not delay referral pending additional imaging - refer simultaneously while ordering MRI to expedite specialist evaluation 1

Differential Diagnosis Considerations

While awaiting definitive diagnosis, the differential includes:

• Soft tissue sarcoma (various subtypes given irregular borders and calcification) 1, 2
• Lymphoma (given axillary location and adjacent lymph node involvement) 1, 3
• Atypical lipomatous tumor (though irregular borders make simple lipoma unlikely) 1
• Infectious/inflammatory process (though 6-month duration without systemic symptoms makes this less likely) 1, 4

The presence of irregular borders, calcification, and lymph node involvement strongly favors a neoplastic process requiring tissue diagnosis. 1, 2