Soft tissue mass

A soft tissue mass is a palpable swelling in the subcutaneous tissue, fascia, muscle, tendon or nerve, outside bone and viscera. Most are benign (lipoma, cyst, ganglion), but a small number are sarcomas, and delay in recognising these worsens outcomes. The distinction between benign and malignant is by size, depth, growth and imaging, not by pain.

Clinical relevance. Benign soft tissue tumours outnumber sarcomas by about 100 to 1. Soft tissue sarcomas account for about 1% of adult cancers, and usually present as a painless enlarging mass. Unplanned excision of an unrecognised sarcoma risks local recurrence and mutilating re-excision. Mechanisms. Proliferation of adipose, fibrous, vascular, neural or muscle cells, accumulation of fluid or keratin (cysts), blood (haematoma), or inflammatory and infective collections.

Classification.

• Superficial (outside the deep fascia) or deep (beneath the fascia, within or between muscles).
• By tissue of origin: adipose, fibrous, vascular, neural, muscle, synovial, cystic.
• By behaviour: benign, locally aggressive (desmoid), intermediate and malignant (sarcoma).
• By tempo: acute (haematoma, abscess), subacute and chronic.

Key distinctions. A deep mass, a mass over 5 cm, a growing mass, or a mass that has recurred after excision is a sarcoma until proved otherwise. Pain is uncommon in sarcoma and does not exclude it.

History.

• Duration, rate of growth, change in size over weeks, pain, night pain, associated swelling of the limb, trauma, and relation to meals, posture, exertion or activity.
• Previous cancer, radiotherapy to the area (radiation induced sarcoma), lymphoedema, chronic ulcer, immunosuppression, HIV, hepatitis, occupational and vinyl chloride exposure.
• Family history of sarcoma, neurofibromatosis, Li-Fraumeni syndrome, familial adenomatous polyposis, and retinoblastoma.
• Fever, erythema, discharge, injection or skin penetration (abscess), anticoagulant use and bleeding disorder (haematoma).
• Weight loss, cough and haemoptysis (lung metastases).

Examination.

• Site, size in two dimensions (measure with a ruler), shape, surface, edge, consistency, tenderness, warmth, skin involvement, pulsation, and transillumination.
• Depth and mobility: mobile in two planes (superficial) or fixed or less mobile when the underlying muscle is tensed (deep). Cough impulse and reducibility for hernia.
• Distal neurovascular status, limb circumference and regional lymph nodes (epithelioid sarcoma, rhabdomyosarcoma, synovial sarcoma and angiosarcoma may spread to nodes).
• Skin for café au lait spots and neurofibromas, Tinel sign over neural masses, and signs of venous malformation.
• Examine for a primary source in a mass that may be metastatic, and note any scar.

Red flags.

• Size over 5 cm, or increasing size.
• Deep location beneath the fascia, or fixed to deep structures.
• Painful mass in a previously painless lesion, or rapid growth.
• Recurrence after previous excision.
• Mass in a previously irradiated field.
• Hard, irregular or ulcerated mass, overlying skin changes, or necrosis.
• Associated neurovascular deficit.
• Fever, erythema, severe pain and systemic illness (abscess, necrotising infection, pyomyositis).
• Pulsatile mass.

Special groups. Children: rhabdomyosarcoma, infantile fibromatosis, haemangioma and lymphatic malformation, and any persistent firm mass needs imaging. Pregnancy: use ultrasound and MRI without contrast. HIV: Kaposi sarcoma, lymphoma, tuberculous abscess and pyomyositis.

Benign tumours.

• Lipoma (commonest), angiolipoma, fibroma, neurofibroma, schwannoma, haemangioma and vascular malformation, lymphatic malformation, glomus tumour, leiomyoma.
• Nodular fasciitis, elastofibroma dorsi, myositis ossificans.

Cystic lesions. Epidermoid (sebaceous) cyst, ganglion, synovial cyst, Baker cyst, bursitis, mucous cyst, branchial and thyroglossal remnants.

Locally aggressive and intermediate. Desmoid fibromatosis, atypical lipomatous tumour, dermatofibrosarcoma protuberans, solitary fibrous tumour.

Malignant.

• Soft tissue sarcomas: liposarcoma, undifferentiated pleomorphic sarcoma, leiomyosarcoma, synovial sarcoma, rhabdomyosarcoma, angiosarcoma, malignant peripheral nerve sheath tumour, epithelioid sarcoma, fibrosarcoma.
• Kaposi sarcoma.
• Lymphoma, metastasis (melanoma, lung, breast, kidney), and primary bone tumours with soft tissue extension (Ewing sarcoma, osteosarcoma).

Inflammatory, infective and traumatic. Abscess, pyomyositis, necrotising soft tissue infection, infected cyst, tuberculous abscess, cystic hydatid disease, cysticercosis, foreign body granuloma, haematoma, fat necrosis, hernia, muscle tear and rupture.

Vascular. Aneurysm and pseudoaneurysm, arteriovenous malformation, varicose vein cluster, lymph node.

Step 1. Decide whether the mass is acute and inflamed (needing drainage), vascular (pulsatile), or a solid lump needing risk stratification. Size over 5 cm, deep location, or growth moves the patient to specialist sarcoma assessment.

Step 2. Ultrasound as the first imaging test in all palpable masses. It identifies cysts, lipoma, ganglion, haematoma, abscess and vascular lesions, and shows solid, heterogeneous, vascular or deep lesions for further imaging.

Step 3. MRI of the whole compartment with and without contrast for any solid mass over 5 cm, deep mass, growing or indeterminate mass, or mass with suspicious ultrasound features. MRI shows size, depth, relation to neurovascular structures and tissue characteristics (fat content, necrosis, haemorrhage). Plain radiographs for calcification or ossification (myositis ossificans, synovial sarcoma, phlebolith).

Step 4. Biopsy before any excision of a suspected sarcoma, planned by or with the sarcoma team after MRI.

• Image directed core needle biopsy (14 gauge or larger, several cores), with the track placed along the planned surgical incision so that it can be excised.
• Avoid fine needle aspiration alone and excisional biopsy of a mass that may be sarcoma. A simple lipoma, ganglion or cyst with benign ultrasound features can be excised without biopsy.
• Immunohistochemistry and molecular tests (for example MDM2 amplification for lipomatous tumours) on core tissue.

Step 5. Staging of confirmed sarcoma: CT chest (lung is the commonest metastatic site), MRI or CT of the primary and regional nodes when indicated, and PET CT in selected cases. Blood tests: full blood count, kidney and liver function, calcium, LDH and HIV test in endemic settings.

Limitations. Ultrasound may not exclude deep or retroperitoneal masses. MRI cannot always separate lipoma from well differentiated liposarcoma, which needs MDM2 testing. A negative core biopsy can reflect sampling error and requires radiological correlation.

Principles. Do not excise a mass that meets sarcoma criteria before imaging and referral. Treat infection and haematoma promptly. Reassure and observe benign lesions.

Abscess.

• Incision and drainage with a wound swab or pus culture, which is the main treatment. Packing is usually unnecessary after small abscesses.
• Add antibiotics for cellulitis, systemic illness, immunosuppression, abscess over 5 cm, face, hands or genitals, or incomplete drainage: flucloxacillin 500 mg to 1 g orally every 6 hours for 5 to 7 days (maximum 4 g daily; reduce the dose in severe kidney impairment); monitor liver tests with courses over 14 days.
• Penicillin allergy or suspected methicillin resistant Staphylococcus aureus: clindamycin 300 to 450 mg orally every 6 to 8 hours for 5 to 7 days (maximum 1.8 g daily; monitor for diarrhoea), or co-trimoxazole 960 mg orally every 12 hours for 5 to 7 days (maximum 1.92 g daily; halve the dose for CrCl 15 to 30 mL/min and avoid under 15 mL/min; monitor potassium, creatinine and rash; avoid in pregnancy and with sulphonamide allergy).
• Severe infection, spreading cellulitis or necrotising infection: piperacillin with tazobactam 4.5 g IV every 6 hours (maximum 18 g piperacillin daily; every 8 hours for CrCl 20 to 40 mL/min and every 12 hours under 20 mL/min) plus clindamycin 600 to 900 mg IV every 8 hours (maximum 2.7 g daily) with urgent surgical debridement. Add vancomycin 25 mg/kg IV loading dose (maximum 3 g) then maintenance dosed by kidney function and levels when MRSA is possible; monitor creatinine and levels.
• Tetanus immunisation status review and booster when needed.

Haematoma. Rest, compression and elevation, and review of anticoagulants and antiplatelet drugs. Ultrasound for a large or enlarging haematoma, and evacuation for tense swelling, compartment syndrome or infection. Correct coagulopathy. A haematoma without clear trauma, or one that does not resolve in 6 weeks, needs MRI (haemorrhage into sarcoma).

Pain. Paracetamol 1 g orally every 6 hours as needed (maximum 4 g daily; 3 g daily if weight under 50 kg, malnutrition, alcohol excess or liver disease). Avoid NSAIDs when bleeding is a risk.

Benign lesions.

• Lipoma, epidermoid cyst and ganglion: observe if asymptomatic. Excise for pain, rapid growth, cosmetic or functional reasons. Epidermoid cyst excision includes the cyst wall and punctum. Ganglion aspiration recurs often, and excision is done for pain or nerve compression.
• Neurogenic tumours: do not biopsy blindly. Refer for imaging and neurosurgical or peripheral nerve review because of the risk of neurological deficit.
• Myositis ossificans: rest and gentle mobilisation, with excision only when mature.

Suspected or confirmed sarcoma.

• Refer to a regional sarcoma service within 2 weeks of the suspicion arising, with imaging and without prior excision.
• Management is multidisciplinary: wide local excision with negative margins, preoperative radiotherapy for large high grade tumours (usually 50 Gy in 25 fractions), and systemic therapy for selected high grade or metastatic disease.
• When an unplanned excision has occurred, provide the operative and pathology record, and arrange MRI before re-excision.

Kaposi sarcoma. Treat HIV with antiretroviral therapy through the HIV service. Chemotherapy for advanced or visceral disease (paclitaxel or liposomal doxorubicin) through oncology.

Monitoring. Follow benign lesions at 3 to 6 months, and re-image if growth occurs. Monitor infected wounds at 48 hours. Surveillance after sarcoma treatment includes examination and chest imaging every 3 to 6 months for 2 to 3 years.

Referral and escalation. Sarcoma service for suspected sarcoma. Orthopaedic or general surgery for benign excision. Vascular surgery for aneurysm. Oncology for metastasis and Kaposi sarcoma. Infectious diseases for necrotising infection or pyomyositis, and HIV services when relevant.

Admission criteria. Necrotising infection, abscess with sepsis, compartment syndrome, large expanding haematoma with haemodynamic effect, neurovascular compromise, and pending urgent staging in a frail patient.

Discharge and safety netting. Discharge benign lesions with a clear description and review plan. Patients return for increasing size, new pain, skin change, fever, spreading redness, numbness or weakness in the limb, or a new lump.