Soft tissue mass

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Introduction

A soft tissue mass is one of the most common manifestations of a musculoskeletal tumor. Proper diagnosis and treatment are essential to avoid the potential for loss of limb function and to maximize the opportunity to cure a soft tissue sarcoma.

History

When obtaining the patient history, consider:

The patient's age. Infants and children may present with benign lesions that can demonstrate local growth, disfigurement, overgrowth of the extremity or loss of function (lipomas, hemangiomas, lymphangiomas, neurofibromas, hamartomas, congenital or infantile fibromatosis). Soft tissue sarcoma is extremely rare in children, but when it occurs, it is most likely to be rhabdomyosarcoma. In adults, rhabdomyosarcoma is rare in the extremities.

The length of time that the lesion has been present. The patient may have had a benign soft tissue lesion for several years that has not grown during that time. He or she may finally decide to "get this bump looked at," or may be encouraged to consult a physician by a spouse or a friend. The pattern of growth is important: A mass that has been present for years and that begins to grow may be transforming from a benign to a malignant lesions, or it may simply be growth of a benign soft tissue tumor. Rapid growth may also indicate that the mass may be malignant. Growth of a soft tissue tumor, therefore, warrants further evaluation..

The presence of pain. Although often tender to direct pressure, a soft tissue tumor itself rarely causes the patient pain. The exceptions are peripheral nerve sheath tumors and rapidly growing soft tissue sarcomas, which may cause pressure on surrounding structures and intra-compartmental compression. If the patient is experiencing pain, also consider other diagnoses, such as infection.

A history of trauma. Chronic repetitive trauma to the soft tissues may cause reactive fibrosis; a more acute, severe injury may suggest myositis ossificans. It is not unusual for a patient to discover a soft tissue mass after a major or minor trauma to the anatomical area -- or to mistakenly believe that the injury caused the lesion. If the mass persists following trauma, a complete workup is needed to establish whether it is related to the trauma (such as a persistent hematoma) or is, in fact, a soft tissue tumor. Ask about a past history of penetrating trauma or infection -- an old soft tissue infection or foreign body reaction may lead to the late presentation of a calcified soft tissue mass.

Possible generalized conditions. Neurofibromatosis is the best example of a generalized disease that may be associated with one or more soft tissue masses. A patient with this disease may present with benign growth of a plexiform neurofibroma, or alternatively, a benign nerve sheath tumor may transform into a neurofibrosarcoma. Multiple soft tissue benign myxomas may develop in a ?patient with extensive fibrous dysplasia of the bones and cafe au lait spots (possibly associated with premature onset of menses in the McCune-Albright syndrome). A patients with Maffucci's syndrome (multiple bone enchondromas associated with soft tissue hemangiomas) may present with transformation of a hemangioma to angiosarcoma.

Family history of soft tissue masses. This is particularly pertinent to the diagnosis of neurofibromatosis. In some cases of familial cancer syndromes (Li-Fraumeni syndrome related to the inheritance of a mutant p53 allele, for example), family members may have a high risk of developing soft tissue sarcoma as well as other forms of cancer.

Physical Examination

The physical examination of a patient with a possible soft tissue tumor includes the following:

Depth. One of the most critical aspects of the physical examination is determining whether a lesion arising deep to dermis is superficial or deep to fascia; most lesions developing superficial to fascia are benign. In making this determination, attempt to move the lesion over the fascia, both before and after the patient tenses the underlying muscle. If the lesion moves with the muscle, it is likely deep to fascia. In some instances, it may be impossible to tell if the lesion is deep or superficial; the lesion may even arise from the fascia. As discussed below, the investigation and management of soft tissue lesions depends on the depth of the mass. Those arising deep to fascia have the greatest risk of malignancy. If the physical examination indicates that the lesion arises in fascia, deep to fascia, or is uncertain, obtain imaging of the mass.

Size. After determining the depth, document the clinical size of the lesion in three dimensions. Evaluate the condition of the overlying tissues, determining whether there is evidence of inflammation that suggests either soft tissue infection or a rapidly growing tumor. Tenderness could also indicate a rapidly growing tumor, a peripheral nerve sheath tumor, or infection. Observe the surrounding skin for evidence of vascular changes that may suggest multiple vascular malformations. Particularly in children, document evidence of extremity overgrowth, including measurement of the extremity length and diameter.

Distal neurovascular status. Test for a nerve deficit or evidence of venous or arterial obstruction by evaluating distal neurovascular status. Soft tissue tumors rarely cause a neurological deficit. Instead, nerve deficit usually indicates that the tumor is arising in the peripheral nerve or is invading the nerve. Examine the skin should for evidence of cafe au lait spots, dermatofibromas, or axillary freckling, which may suggest neurofibromatosis or, in the case of cafe au lait spots, fibrous dysplasia.

Regional nodes. Palpate the regional nodes, although soft tissue sarcomas rarely metastasize by lymphangitic spread. Rhabdomyosarcoma and synovial sarcoma are the most likely diagnoses if nodal metastases are found. Examine the other extremities and trunk for soft tissue masses; lipomas -- and less commonly liposarcoma -- may present in multiple sites. Advanced metastatic carcinoma or lymphoma may spread to the non-nodal soft tissues; therefore, evidence of a primary cancer elsewhere must be evaluated on both history and physical examination.

Dermatological lesions. The only dermatological lesion related to musculoskeletal tumors is dermatofibrosarcoma protuberans. This lesion is elevated above the dermis, purplish in color, and characteristically develops satellite nodules as it grows. It behaves like a low-grade soft tissue sarcoma and is generally managed in a similar manner. Subcutaneous malignant fibrous histiocytomas may also result in invasion of the dermis, but generally malignant mesenchymal lesions do not develop primarily in the skin.

Investigations

Results of the history and physical examination will guide the next steps:

Lesion Less than 5 cm in Diameter

Observation is appropriate for this size lesion if it is also soft in consistency, superficial to fascia, not enlarging, and not cosmetically or functionally troubling. Measure and record the size of the lesion annually for 2 or 3 years.

If a lesion this size bothers the patient or is firm, painful, or enlarging, it can generally be removed by excisional biopsy, taking care to avoid violating the underlying fascia. Send the specimen for appropriate pathological analysis, and if the pathologist determines it to be a soft tissue sarcoma, locally curative management can then be achieved by re-excising the surgical scar and incorporating the fascia as a deep margin. Avoid excisional biopsy and obtain imaging and a needle or incisional biopsy prior to excision if the lesion is located in an anatomical region that would preclude later re-excision (for example, if a small lesion is located directly over the bone in the subcutaneous tissues overlying the ulna or tibia).

Superficial Lesion Larger than 5 cm in Diameter

Before attempting excision, evaluate a lesion this size by magnetic resonance imaging (MRI). MRI is more appropriate for evaluating soft tissue tumors than computerized tomography (CT) scan because the enhanced soft tissue contrast of MRI allows for optimal demarcation of the lesion from surrounding normal soft tissues and for assessment of possible neurovascular involvement. It is likely that a superficial lesion greater than 5 cm is lipoma. If this is confirmed by MRI, the lesion may be observed or treated by excisional biopsy, depending on growth characteristics and patient preference.
Needle or incisional, rather than excisional, biopsy should be undertaken if the lesion does not demonstrate a lipoma's typical well-demarcated, homogeneous pattern of fat on MRI, or if there are any regions of high (bright) T2-weighted signal within the fat of the tumor. Critically evaluate whether there is any evidence of edema surrounding the superficial tumor. If the margin with normal surrounding subcutaneous fat is not sharp and discrete on MRI, a biopsy should be done prior to excision.

Lesion Attached to Fascia, Deep to Fascia, or Depth Unknown

MRI should be undertaken to diagnose the lesion. The potential diagnoses for deep lesions include benign conditions (intramuscular lipoma, hemangioma, myxoma, benign peripheral nerve sheath tumor), benign aggressive tumors likely to recur locally after simple excision (fibromatosis, hemangiopericytoma), and soft tissue sarcoma. Effective treatment of many of these lesions will include wide surgical excision, and the likelihood of achieving adequate surgical removal with minimal functional deficit is enhanced if the patient is initially evaluated with MRI and carefully planned biopsy. Conversely, it may be very difficult to perform adequate surgical excision with conservation of function if the initial treating physician performed an excisional biopsy of a subfascial sarcoma, which would cancer cells throughout the extremity. If the depth of the lesion is not apparent on physical examination, the clinician should err on the side of ordering imaging before attempting a biopsy.

Suspected or Confirmed Diagnosis of Soft Tissue Sarcoma

In these cases, metastatic staging with chest CT is necessary. Lymphatic spread to nodal groups may be assessed clinically and, if suspected, assessed by CT scan.

If there is a history of trauma in a patient with a soft tissue mass, plain radiographs may demonstrate the typical peripheral ossification pattern seen in myositis ossificans. In most cases of soft tissue masses however, plain radiographs are of little value, although they may demonstrate increased soft tissue lucency caused by a large fatty lesion or the calcification occasionally observed in lipomas, liposarcomas, or synovial sarcomas. Bone scans are not useful in most cases either, since soft tissue tumors rarely invade the bone cortex. If the bone cortex is invaded, a CT scan may be more useful than either a bone scan or an MRI because a CT scan usually gives the best anatomical definition of the extent of bony destruction. In general, though, MRI is the most effective imaging modality for soft tissue masses.

Blood work is not usually helpful in the diagnosis of soft tissue masses, although a complete blood count, ESR and C-reactive protein may be helpful if infection is suspected. Patients with myositis ossificans or soft tissue osteosarcoma may have an elevated serum alkaline phosphatase.

Conclusion

In summarizing the investigation of patients with soft tissue masses, the following guidelines are suggested:

If the lesion originates in or deep to fascia, or if the depth is uncertain, cross-sectional imaging should be ordered.

If the lesion is superficial to fascia and larger than 5 cm, imaging should be undertaken. In our experience, MRI is preferred to CT. However, if MRI is not available, CT is often sufficient for initial investigation.

After localizing the lesion anatomically, it is necessary to obtain a biopsy of most deep lesions. An initial biopsy for superficial lesions that are greater than 5 cm is also suggested. Deep soft tissue lesions should never be treated with an excisional biopsy. Doing so makes definitive management much more difficult and therefore should be avoided.

The Other Presenting Complaints