Essentials of Orthopedic Surgery, third edition / 04-Tumors of the Musculoskeletal System

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FIGURE 4-21. Process taken when evaluating a patient presenting with a soft-tissue mass.

eate the cross-sectional anatomic extent and compartmentalization of the lesion. Unique features of modern MRI, including use of gadolinium contrast, mixed spin-echo images, and fat-suppression images, appear to facilitate visualization of tumor extent and may prove crucial to longitudinal study of postoperative patients to allow for early detection of local recurrences (Fig. 4-22).

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Angiography

Biplane angiography remains the standard technique for demonstrating the position of the major vessels. Although MRI and contrast-enhanced CT often show the vessels, angiography is helpful in planning an operative approach, especially if displacement is noted on the CT scan (Fig. 4-23).

Bone Scans

Bone scintigraphy is used to determine the relation of adjacent bony structures to the tumor. Increased contrast-medium uptake by a bone in close proximity to a STS usually indicates a reactive rim of tumor near the periosteum, rather than direct intraosseous tumor extension.

Treatment

The treatment of high-grade STS has undergone fundamental changes within the past decade. Treatment of these patients requires a multimodality approach, and successful management requires cooperation of the surgeon, chemotherapist, and radiation oncologist. The appropriate role of each modality is continuously changing but can be described in general as follows.

FIGURE 4-22. Sarcoma of leg. MRI scan demonstrates a large soft tissue mass of the posterior leg (soleus muscle). This lesion has compressed the surrounding anatomical structures and has a heterogeneous appearance.

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FIGURE 4-23. Angiogram demonstrates an incredibly vascular soft tissue tumor arising in the thigh. The superficial femoral artery serves as the main blood supply for this sarcoma.

Chemotherapy

Combination chemotherapy has been shown to be more effective in preventing pulmonary dissemination from high-grade sarcomas than singleagent therapy. The most effective drugs in use today are doxorubicin hydrochloride (Adriamycin) and ifosfamide. Dacarazine (DTIC), methotrexate, and cisplatin also have activity and are included in many current protocols. The various combinations are traditionally given in an adjuvant (postoperative) setting and are presumed effective against clinically undetectable micrometastases. Neoadjuvant (preoperative) chemotherapy is being evaluated in several institutions. Early results have indicated that significant reduction in tumor size can occur, thereby facilitating attempts at limb salvage.

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Radiation Therapy

Radiation typically consists of 5,000 to 6,500 cGy over many fractions. This modality is effective in an adjuvant setting in decreasing local recurrence following nonablative resection. The degree to which the initial surgical volume should be decreased in these circumstances is controversial, although the local recurrence following a wide excision and postoperative radiotherapy is 5% to 10%. The technique of radiation therapy includes irradiating all the tissues at risk, shrinking fields, preserving a strip of unirradiated skin, and using filters and radiosensitizers. Local morbidity has been greatly decreased within the past decade. Preoperative radiation is effective in reducing tumor volume but is associated with increased morbidity resulting from significant wound-healing complications.

Surgery

Removal of the tumor is necessary to achieve local control; this may be accomplished either by a nonablative resection (limb salvage) or by an amputation. The procedure chosen depends on results of the preoperative staging studies. A prospective randomized National Cancer Institute (NCI) trial established that a multimodality approach employing limb salvage surgery combined with adjuvant radiation and chemotherapy offered local control and survival rates comparable to those of amputation plus chemotherapy while simultaneously preserving a functional extremity.

The use of adjuvant therapy (chemotherapy or radiation) permits limbsparing procedures for the majority of extremity soft tissue sarcomas. Enneking has shown that a radical resection for an STS has about a 5% local recurrence rate with surgery alone.3,4 Wide excision (without adjuvant radiation or chemotherapy) has a 50% rate of local failure. Results from the NCI showed that the rate of local recurrence decreased to 5% following local excision (either a marginal or wide excision) when combined with postoperative radiation therapy and chemotherapy. Others have reported similar good results from preoperative radiation, with or without preoperative chemotherapy. Contraindications to limb-sparing surgery are similar to those for the bony sarcomas. In general, nerve or major vascular involvement is a contraindication.

Studies of referred patients show that approximately half of all patients with soft tissue sarcomas treated with attempted excisional biopsy by the referring surgeon have remaining microscopic or gross tumor. As a result, referred patients undergo routine reresection of the surgical site to ensure adequate local control before institution of adjuvant treatment.

General Surgical Technique and Considerations

The general surgical and oncologic principles are as follows:

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1.All tissue at risk should be removed with a wide, en bloc excision that includes the tumor, a cuff of normal muscle, and all potentially contaminated tissues. The 1entire muscle group need not be removed. The biopsy site should be removed with 3 cm of normal skin and subcutaneous tissue en bloc with the tumor.

2.The tumor or pseudocapsule should never be visualized during the procedure. Contamination of the wound with tumor greatly increases the risk of local recurrence.

3.Distant flaps should not be developed at the time of resection, as this may contaminate a noninvolved area.

4.The margin surrounding the surgical wound should be marked with metallic staples. The staples help the radiotherapist determine the highrisk area, should radiation treatment be needed later.

5.Reconstruction of the defect should include local muscle transfers to protect exposed neurovascular bundles and bone cortex.

6.All dead space should be closed, and there should be adequate drainage to prevent hematoma.

Perioperative antibiotics should be given. These procedures have a low but significant rate of postoperative infection. The risk of infection following preoperative adjuvant therapy is particularly high.

Specific Soft Tissue Sarcomas

The five most common soft tissue sarcomas are briefly described next.

Malignant Fibrous Histiocytoma

Malignant fibrous histiocytoma (MFH), first described as a specific entity in 1963, is the most common STS in older adults. MFH occurs in primarily in adults and is most prevalent in the lower extremity, followed in frequency by the upper extremity and retroperitoneum. The histologic grade (usually intermediate to high grade) is a good prognosticator of metastatic potential. The myxoid variant, particularly when located in the superficial soft tissues, tends to have a more favorable prognosis than the other subtypes. In fact, the pure myxoid tumors with bland spindle cells are considered to be low-grade neoplasms with minimal metastatic potential. It has been suggested that high-grade pleomorphic MFH are a heterogeneous collection of poorly differentiated sarcomas, many of which can be specifically classified with the application of immunohistochemical and electron microscopic techniques.

Liposarcoma

Liposarcoma is the second most common STS. It has a wide range of malignant potential dependent upon the grade of the individual tumor.

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Determination of subtype and grade is essential to appropriate management. Well-differentiated (grade I) liposarcomas rarely metastasize. Unlike other sarcomas, liposarcomas may be multiple and may occur in unusual sites within the same individual. Careful evaluation of other masses in a patient with a liposarcoma is mandatory. Occasionally, these lesions occur in children. Liposarcomas very rarely arise from preexisting benign lipomas.

Fibrosarcoma

Fibrosarcoma used to be considered the most common STS. Following the identification of MFH as a distinct entity and the establishment of reproducible criteria for the recognition of other definitive spindle cell sarcomas, fibrosarcoma is less commonly diagnosed. Clinical and histologic difficulty occasionally arise in differentiating low-grade fibrosarcoma from fibromatosis and its variants. The anatomic site, age, and histologic findings must be carefully evaluated. This is a neoplasm of midadulthood and most commonly affects the lower extremity.

Synovial Sarcoma

Synovial sarcomas are the fourth most common STS. They characteristically have a biphasic pattern that gives the impression of glandular formation, which was originally thought to be indicative of synovial origin. These tumors, however, rarely arise within a joint, but rather have a distribution similar to those of other STS. Uncommon primary sites include the retropharynx, orofacial area, and retroperitoneum. Synovial sarcomas occur in a younger age group than other sarcomas; 72% of patients in one large study were below the age of 40 years. There is a propensity for the distal portions of extremities: hand (5%), ankle (9%), or foot (13%). The plain radiograph often shows small calcifications within a soft tissue mass; this should alert the physician to the diagnosis. Lymphatic spread occurs occasionally (5%–7%). Virtually all synovial sarcomas are high grade.

Epithelioid Sarcoma

Epithelioid sarcoma was first described in 1970. It is an unusually small tumor that is often misdiagnosed as a benign lesion. Half these lesions occur in the forearm and wrist, and it is the most common sarcoma of the hand. This lesion has a propensity for eventual lymph node involvement.

Rarely, it presents as a metastasis to the epitrochlear lymph node. In contrast to other sarcomas, it occurs predominantly in adolescents and young adults (average age, 26 years). When it arises in the dermis, in which case it presents as a nodular or ulcerative process, it often clinically simulates benign cutaneous diseases, such as granulomatous dermatitis.

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Benign Soft Tissue Tumors

All mesenchymal tissue can give rise to benign lesions. They may occasionally be confused with malignant lesions, or they may become symptomatic because of their size, anatomic location, or both. Although these tumors are benign, local recurrence or difficult anatomic location can cause significant morbidity. Some, such as lipomas, are easily cured by simple removal, while others, most notably fibromatoses, require extensive resection. Thus, it is important to differentiate these lesions from their malignant counterparts, establish a correct diagnosis, and remove them surgically.

There are a large number of benign lesions. The more-common lesions and their unique characteristics are described.

Benign Adipose Tumors

Simple Lipoma

Lipomas, the most common mesenchymal neoplasms, arise from normal fat and appear during adulthood. They may be single or multiple; the latter occur in only 5% of all patients. They are found either subcutaneously or deeply embedded. Eighty percent of all lipomas are of the simple type. The shoulder girdle and proximal thigh are the two most common sites. Simple surgical excision is curative (Fig. 4-24).

Microscopic Characteristics

Both types of lipomas consist of monotonous sheets of mature fat cells that are ovoid to round and usually contain a single fat droplet that compresses the nucleus along the cell membrane. Capillary-like vessels occasionally appear between the fat lobules. Areas of myxoid change or dense fibrous trabeculae are sometimes seen.

Spindle Cell Lipoma

This is a variant of lipoma consisting of benign spindle cells in addition to mature fat. The tumor has a predilection for males (90%) and most commonly occurs in the neck and shoulder. Spindle cell lipomas are encapsulated and are easily removed by simple excision. It is essential to distinguish this lesion clinically from a well-differentiated liposarcoma.

Pleomorphic lipomas also consist of mature fat cells, but they are more variable in size. They contain both pleomorphic and distinctive multinucleated giant cells instead of spindle cells. These giant cells contain multiple overlapping nuclei at their peripheries. Occasionally, lipoblast-like cells occur.

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FIGURE 4-24. Lipoma. Clinical photograph of a large lipoma of the distal portion of the biceps muscle of the arm. Lipomas tend to be slow growing and are frequently asymptomatic to the patient. Lipomas are the most common soft tissue tumors of the extremities. Lipomas never become malignant.

Intramuscular and Intermuscular Lipomas

Lipomas occurring within (intramuscular) and between (intermuscular) muscle groups often become large, produce few symptoms, and present as a mass mimicking an STS. Clinical evaluation and staging are similar to those of any suspected sarcoma. The pathologist must be aware of the clinical setting, and an adequate sample must be obtained to differentiate a low-grade liposarcoma from a true benign lipoma. In contrast to superficial lipomas, these lesions often do not have a capsule and tend to infiltrate the surrounding muscle. A marginal or wide resection is required to obtain local control. These lesions never become malignant (Fig. 4-25).

Benign Tumors of Peripheral Nerves

The two most common nerve tumors are neurilemmoma and neurofibroma.

Neurilemmoma (Schwannoma)

These benign growths arise within a nerve and are surrounded by a true capsule composed of the epineurium. They are composed of Antoni A (cellular) and Antoni B (loose myxoid) components. These lesions generally are not associated with von Recklinghausen’s disease (multiple

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FIGURE 4-25. Lipoma. MRI demonstrates an intramuscular lipoma. Note that the tumor has approximately the same level of enhancement as the normal subcutaneous fat, with no heterogeneosity noted, as is characteristic of all lipomas.

neurofibromatosis). Surgical treatment entails opening the capsule and enucleating the growth from the nerve. “Ancient” neurilemmoma is cystic degeneration of a neurilemmoma. These lesions clinically present as a large mass with some cellular atypia. They must be differentiated from malignant lesions. Simple excision, done for diagnostic purposes or if the lesion is symptomatic, is curative.

Neurofibroma

Neurofibromas may be solitary or multiple. In contrast to neurilemmomas, they are not encapsulated. They often enlarge the nerves and may undergo malignant degeneration. Histologically, they consist of Schwann cells associated with collagen fibrils and myxoid material. Multiple neurofibromas are found in patients with von Recklinghausen’s disease. These lesions cannot be surgically detached from the underlying nerve. Surgery is indicated only if malignant degeneration is suspected. Between 20% and 65% of patients with neurofibromatosis ultimately develop a sarcoma.

Benign Fibrous Tumors

There are a large variety of benign fibrous tumors. Most are treated by simple excision. Aggressive fibromatosis is a benign but locally aggressive lesion deserving special consideration.

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Aggressive Fibromatosis

This tumor, which appears bland microscopically, is the most serious of all the benign soft tissue tumors. It does not have a capsule and tends to infiltrate far beyond its clinically recognized boundaries. This lesion does not respect fascial borders and thus can attain a large size and involve multiple anatomic compartments if left untreated. The most common locations are the neck, shoulder, and pelvic girdle. Death results from intrathoracic or retroperitoneal extension. The clinical history often reveals multiple recurrences despite supposedly adequate surgical removal. The appropriate surgical procedure is wide excision. Local recurrence uniformly follows excision with positive margins. Surgical staging studies should be performed before resection. Amputation is occasionally required. Radiation and chemotherapy have recently been used for unresectable fibromatosis.

Benign Vascular Tumors

Hemangioma

Benign tumors of the blood vessels consist of a variety of hemangiomas. It is not certain whether these are true neoplasms, hamartomas, or vascular malformations. There are two types of hemangiomas, generalized and localized; the latter are more common. Hemangiomas are classified on the basis of their pathologic appearance—capillary, cavernous, venous, or arteriovenous. Capillary hemangiomas are the most common type. Most hemangiomas occur during childhood. Venous hemangiomas occur during adulthood and are often deeply situated. Intramuscular hemangiomas are rare and are occasionally difficult to differentiate from angiosarcomas. Evaluation requires angiography and venography. Surgery is indicated if symptoms develop. Hemangiomas rarely become malignant.

Angiomatosis is a benign condition characterized by involvement of multiple types of mesenchymal tissues. Large anatomic regions, even an entire limb, may be affected. These extensive vascular lesions, which are probably hamartomatous, can involve the skin, subcutaneous fat, skeletal muscle, fascia, and bone. Involvement of an entire extremity can cause hypertrophy of the limb.

Suggested Readings

1.Malawer M, Sugarbaker PH (eds) Musculoskeletal Cancer Surgery: Treatment of Sarcomas and Allied Diseases, 1st ed. Dordrecht: Kluwer, 2001.

2.Enneking WF, Spanier SS, Malawer MM. The effect of the anatomic setting on the results of surgical procedures for soft parts sarcoma of the thigh. Cancer (Phila) 1981;47(5):1005–1022.