Soft tissue mass

Soft tissue masses or lesions are a common medical condition seen by primary care physicians, family physicians, surgeons and orthopaedists. They include all soft tissue outgrowths benign and malignant ^1-3.

Epidemiology

Soft tissue masses are very common, with benign lesions being much more frequent than their malignant counterparts, outnumbering them by about 100-150 to one ^1-4. Benign soft tissue neoplasms occur with an estimated incidence of approximately 3000/million as opposed to soft tissue sarcomas, which are much less frequent and with an estimated incidence of about 50/million ⁴. Sarcomas can occur at any age and are generally more common in older people ^1,2. However, the ratio of malignant versus benign soft tissue lesions is higher in children because benign lipomas and epidermal cysts are infrequent in that population ¹. 

Many lesions remain unrecognised since not all patients do seek medical attention if they are asymptomatic ².

Associations

Soft tissue masses might be associated with the following ²:

• trauma
• infection
• cancer

Diagnosis

The diagnosis of soft tissue masses is established by a combination of clinical information (comprehensive history and physical examination), imaging findings and histology when indicated ³.

Worrisome features that should raise suspicion for malignancy include ^1,3,4:

• large size >5 cm
• deep location in relation to the vesting fascia
• sudden onset and/or rapid growth
• firm consistency compared to muscle
• adherence to surrounding structures

Definite diagnosis is usually established histologically ³.

Clinical presentation

The clinical presentation of soft tissue masses can provide important clues to the aetiology of soft tissue masses and important features are the time the mass is present, size, depth, mobility and consistency as well as changes in size and growth rate, the duration, the type of associated symptoms and any prior history of trauma, inflammation/infection or cancer ^1-3.

Laboratory studies are usually not of significant benefit because they are unspecificnon-specific in the evaluation of soft tissue masses ^1-3. Inflammatory markers might be abnormal in the setting of an infectious or inflammatory process, uric acid might be elevated in the setting of gout ³.

Certain symptoms and potential corresponding conclusions/clues ^1-3:

• slow growth rather suggests benign aetiology, whereas a fast-growing mass is more worrisome for malignancy
• changes in size (waxing and waning):  suggestive for ganglion cyst or haemangioma but uncharacteristic for sarcoma ^2,3
• superficial bruising and ecchymosis: suggests traumatic haematoma
• warmth and tenderness: typically indicate an inflammatory or infectious origin
• constitutional symptoms: can come with infection and malignancy
• firm consistency: e.g. desmoid tumour
• Tinel sign: suggestive of peripheral nerve sheath tumours
• pain: relatively unspecific
• usually present: abscess or tenosynovial giant cell tumour
• might occur: different soft tissue tumours such as haemangioma, peripheral nerve sheath tumours, desmoid tumour
• unusual or absent: soft tissue sarcoma (unless they are large), lipoma ⁴

Complications

Complications of soft tissue masses include nerve compression syndromes.

Pathology

The pathology of soft tissue masses varies with the aetiology. Biopsy of suspicious soft tissue masses is technically demanding-demanding and requires careful planning due to the potential complications including needle tracttrack seeding. There are two general forms of soft tissue biopsy ^2,3:

• needle biopsy
  • fine needle aspiration (FNA)
  • core needle biopsy (CNB)
• open biopsy
  • incisional biopsy
  • excisional biopsy: in small tumours that are thought to be benign such as lipoma or peripheral nerve sheath tumour

The needle tracttrack should pass through tissue that will be excised during the definite surgery away from major neurovascular structures and in and in case muscles have to be crossed, those involved by the tumour ¹.

Aetiology

The most common aetiologies of soft tissue masses include the followingare ^1-5:

• benign neoplasms: lipoma, neurofibroma, tenosynovial giant cell tumour, haemangioma
• malignant neoplasms: soft tissue sarcoma, metastatic cancer, lymphoma
• inflammatory masses: gouty tophus,  rheumatoid nodules, epidermal inclusion cyst
• infection: abscess, tuberculosis, hydatid cyst
• traumatic: haematoma, myositis ossificans, Morel Lavallée lesion
• vascular: aneurysm, pseudoaneurysm, arteriovenous malformation
• congenital: accessory muscle

Location

Soft tissue masses can be located anywhere in the body, they can be distinguished based on their depth in superficial and deep soft tissue masses. A superficial location is often but not always indicative of a benign dignity whereas deeply situated masses should raise suspicion for malignancy ².

Classification

Soft tissue masses might be classified into mesenchymal tumours and non-neoplastic soft tissue tumours. Soft tissue neoplasms have been classified by the World Health Organisation with regard to the tissue of origin ^1,4: see the WHO classification of soft tissue tumours

Radiographic features

Certain imaging findings and their corresponding conclusions/clues ³:

• calcified phleboliths: haemangioma
• mature trabecular bone: myositis ossificans

Plain radiograph

Plain radiographs are of limited use for the evaluation of soft tissue masses and usually show only soft tissue shadowing. But they can show calcifications as well as bony involvement in the form of osteolysis, cortical erosion or periosteal reaction.

Ultrasound

Ultrasound can help to specify the size, location and mobility of soft tissue masses as well as in the differentiation of cystic versus solid lesions and to determine vascularity and compressibility ³.

Ultrasound canmay also be also used intra-operativelyintraoperatively to guide biopsy or excision ².

CT

CT can identify calcifications and osseous involvement. It can help in the differentiation of calcifications from ossifications thus chondroid matrix from an osteoid matrix or characterise masses in patients who cannot undergo MRI ². It is also very useful for the evaluation of soft tissue masses of the trunk and in the staging of malignant disease ⁴.

MRI

MRI is considered the imaging modality of choice for the evaluation and tissue characterisation of soft tissue masses ^1-4. It can aid in the differentiation of watery, fatty and solid tumour components and with the administration of contrast in the differentiation of cystic lesions and myxoid neoplasms ³. It helps in the localisation of tumours within the different anatomic compartments and the determination of their relationship to neurovascular structures and the muscular fascia ² and can be used to guide biopsy ³.

Certain MR imaging characteristics of soft tissue masses and corresponding conclusions/clues ³:

• low T1, high T2 with rim enhancement: cystic lesion e.g. ganglion cyst, epidermal inclusion cyst
• low T1, high T2 with a homogenoushomogeneous enhancement: myxoid lesion e.g. intramuscular myxoma
• low T1, high T2 with a heterogenousheterogeneous enhancement: myxoid lesion e.g. myxoid liposarcoma
• early, vivid enhancement: viable solid tumour
• delayed enhancement: granulation tissue
• blooming artifact: the presence of haemosiderin e.g. in haematoma, tenosynovial giant cell tumour, haemangioma

Nuclear medicine

PET-CT can provide information about the metabolic activity of soft tissue tumours and can be used in the evaluation of treatment and the detection of tumour recurrence ^2,3.

Radiology report

The radiological report should include a description of the following points:

• form, location and size, consistency (cystic versus solid)
• tumour margins
• relation to the muscular fascia
• relationship to bones, tendons and joints
• relationship to local nerves and vessels

Treatment and prognosis

Management of soft tissue masses requires careful planning and often consists of resection of the mass with or without adjuvant therapy. Nevertheless, a high percentage of malignant soft tissue masses end up undergoing unplanned resection potentially leading to higher local recurrence rates and other complications ¹.

Four general types of oncologic resection procedures are performed ^2,3:

• intralesional excision: e.g. for haematoma 
• marginal excision: e.g. for lipomas, tenosynovial giant cell tumours, neurofibromas
• wide resection: for locally aggressive tumours such as sarcomas
• radical resection: rarely required

Depending on the aetiology of the soft tissue mass and the type of resection treatment might be combined with different adjuvant or neoadjuvant therapies including local treatment such as cryotherapy or radiofrequency ablation, radiation therapy and chemotherapy ^2,4.

Practical points

Biopsy

• should be done by an oncologic surgeon and ideally by the same surgeon who will definitely treat the patient or perform the excision due to potential complications including tumour cell spreading ^2,3
• should be performed through a single tracttrack that can be completely excised during definitive tumour resection away from nerves and vascular structures ^2-4
• should involve a minimal amount of the overlying skin ¹