Lumps and bumps on the extremities and trunk are common presentations to physicians and surgeons. These growths range from benign neoplasms and cystic structures based in the epidermis and dermis to malignant neoplasms arising within the structures below the deep fascia. These soft-tissue lesions are classified according to the direction of differentiation of the mesenchymal tissue (Table I). Most soft-tissue lesions are benign; however, benign and malignant soft-tissue lesions can present in a similar fashion. In addition, the diverse lesions within the classification system and the unfamiliarity of many pathologists with soft-tissue lesions may make the correct diagnosis difficult. The annual incidence of new sarcoma cases in the United States is about 5000. While Enzinger and Weiss11 suggested that there are at least 100 benign soft-tissue tumors for every malignant tumor examined by a pathologist, the incidence of benign lesions is unknown. This heavy preponderance of benign lesions in patients presenting for medical care mandates that any physician who is planning to treat or excise such lesions be familiar with the characteristics of the potentially malignant mass in order to avoid compromising optimum treatment. Sarcomas may occur in the head and neck areas, the trunk, or the extremities. The buttock and thigh are the most common locations of the most frequent soft-tissue sarcomas. As many of these lesions occur in the extremities, the orthopaedist will see many of these patients and be expected to provide an appropriate workup, referral, or definitive treatment. Soft, mobile, well defined subcutaneous masses are usually benign. In general, one should consider any mass below the deep fascia as potentially malignant, particularly if the mass is firm and immobile. Soft-tissue neoplasms are not necessarily painful and may grow to a relatively large size in the buttock, shoulder girdle, or thigh before they are obvious to the patient. A history of rapid growth usually suggests a malignant process. However, characteristics evident on modern imaging studies may define the lesion as benign rather than malignant. We will describe the management of patients who have a soft-tissue mass, the classification and staging of benign neoplasms, and the common characteristics and recommended treatment of the most frequently encountered lesions as well as some of the more troublesome, less common lesions.
Patients generally are seen with either a painless or painful soft-tissue mass. The clinician should record an in-depth history with particular emphasis on the following questions.
1. How long has the mass been present and is it enlarging?
A new mass that is rapidly increasing in size suggests a malignant tumor. In children and young adults, rhabdomyosarcoma, soft-tissue Ewing sarcoma, and primitive neuroectodermal tumors may increase in size very rapidly. Malignant tumors (such as synovial sarcoma and epithelioid sarcoma) may occasionally present insidiously as small tumors that have been present for a long time. In adults with benign lipomas, there is often a long history of a mass of constant size or of very slow enlargement.
2. Is the mass causing pain?
Most inactive benign lesions are not associated with discomfort. Large, malignant lesions usually cause moderate discomfort when they attain a large size (more than ten centimeters). Very discrete, pinpoint discomfort is often caused by neural lesions (neuroma or neurofibroma) or glomus tumors. Benign lesions may compress peripheral nerves and cause neurological symptoms2.
3. Is there a history of trauma?
Heterotopic ossification may occur following a single traumatic event or repetitive episodes of blunt trauma1. Penetrating trauma can result in a false aneurysm or a hematoma. Foreign bodies may result in granulomas or soft-tissue infections.
4. Is there a history of cancer?
Malignant neoplasms may metastasize to soft tissues and present as undiagnosed masses. Carcinomas of the lung, pancreas, and breast, as well as lymphomas, often metastasize to the skin or subcutaneous tissue.
5. Is there a history of systemic signs and symptoms or of abnormal laboratory findings?
Fever, chills, anorexia, and weight loss may occur with either neoplasms or infections. Several malignant tumors, such as angiomatoid malignant fibrous histiocytoma, angiosarcoma, and soft-tissue Ewing sarcoma, may result in anemia.
The physical examination should include the region of interest, the regional and major lymph nodes, and the abdomen.
The size, character, and mobility of the mass should be recorded. Lesions that are firm, deep (below the fascia), and more than five centimeters in diameter should be suspected of malignancy. On occasion, small, superficial, and mobile masses can also be malignant. For example, epithelioid sarcoma most commonly occurs in the upper extremity, especially the hand, and typically presents as a small nodule on the extensor surface that may ulcerate. This lesion may be confused with a rheumatoid nodule or a foreign-body granuloma. Clear-cell sarcoma may present as a small nodule that occurs along a tendon sheath. Subcutaneous lipomas are usually soft when palpated, whereas sarcomas are usually firm. In contrast, intramuscular lipomas often feel firm, simulating a sarcoma. Angiolipomas are often painful to palpation. Extra-abdominal desmoid tumors have a distinctive, rock-hard character.
Hemangiomas usually have a distinctive presentation. Patients often complain of a mass that aches, especially after the patient has been standing for a prolonged time. When the patient is examined in the supine position, no mass or swelling may be detected. When the patient stands for a few minutes, a discrete or diffusely swollen area will appear as the lesion fills with blood.
The regional lymph nodes should be examined carefully. Synovial sarcomas, epithelioid sarcomas, and rhabdomyosarcomas may spread to regional lymph nodes11. The other major lymph-node-bearing areas (axillary, cervical, and inguinal) should also be examined. Furthermore, adenopathy may indicate lymphoma or metastatic carcinoma.
When the character of the soft-tissue mass is not clearly defined by the history and physical examination, and particularly if it appears to be deep to the subcutaneous tissue, the first imaging study should be a conventional radiographic examination. Plain radiographs are made in two planes. The radiographs are carefully studied to detect mineralization within the soft-tissue lesion and changes in the underlying bone. Both benign and malignant entities may undergo mineralization. Benign lesions that may contain mineralized areas include heterotopic ossification, lipomas, chondromas, and hemangiomas. In patients with heterotopic ossification, the mineralization begins peripherally, with the center of the lesion remaining lucent1. Lipomas may contain islands of mature bone, chondromas usually have stippled areas of calcification, and hemangiomas often have small phleboliths.
Synovial sarcoma, liposarcoma, and soft-tissue osteosarcoma are the principal malignant lesions that may have extensive mineralization. In synovial sarcoma, the mineralization pattern is usually at the periphery of the lesion11. There may be areas of calcification or islands of bone. Liposarcoma may also have mature islands of bone. Osteosarcomas have large areas of mineralized osteoid.
Magnetic resonance imaging has become the modality of choice to define the anatomy of soft-tissue tumors6,7,14,16-18,23. On the basis of signal characteristics, several lesions—lipomas, hemangiomas, and ganglion cysts—can be accurately diagnosed with a high and reliable degree of specificity.
Lipomas have signal characteristics that exactly match the subcutaneous fat on all sequences. There may be small areas of fibrous stranding. Lipomas are well demarcated and do not invade or penetrate fascial boundaries. They lack the centripetal growth pattern of sarcomas and often form tails or irregularly shaped areas where they squeeze into intermuscular planes or adventitial spaces (Figs. 1-A and ( 1-B).
Hemangiomas contain many flow voids, which represent small or large blood vessels3-5. Variable amounts of fat signal are also seen. Hemangiomas may involve muscle or subcutaneous tissue, or both (Fig. 2). Often one or two distinct muscles are involved.
Ganglion cysts have a characteristic appearance on T2-weighted images, with a bright signal that encompasses the entire lesion. The lesions usually have a rounded shape and may be multilocular (Fig. 3).
Post-traumatic conditions (heterotopic ossification, hematomas, and avulsion fractures) often have a characteristic appearance, and the diagnosis can be made after magnetic resonance imaging when the clinical, radiographic, and magnetic resonance features are combined.
When the nature of the lesion is not known, the soft-tissue mass is judged to be indeterminate. A biopsy is usually necessary to establish a histological diagnosis of an indeterminate mass.
There are three techniques for the biopsy of soft-tissue masses: needle biopsy, open incisional biopsy, and open excisional biopsy. The biopsy must be planned carefully to ensure that the orientation of the incision is correct; that adequate tissue is obtained; and that complications, such as infection, wound necrosis, and contamination of critical structures (for example, neurovascular bundles, joint cavities, and internervous planes), are avoided15,21,22.
There are two types of needle biopsy: fine-needle aspiration and core needle biopsy. Fine-needle aspiration can be performed with local anesthesia and minimum morbidity. Unfortunately, few pathologists can confidently identify and classify soft-tissue lesions with the limited quantity of tissue that is obtained with this technique.
Core needle biopsy is a useful procedure in musculoskeletal tumor centers, where experienced pathologists and surgeons are familiar with the proper method of needle placement, the interpretation of frozen sections, and the special handling methods for specimens. This procedure can be performed in an outpatient setting with local anesthesia when the mass is easily palpable or subcutaneous. We prefer to use a 14-gauge needle with a cutting sleeve (Figs. 4-A and 4-B). It usually provides an adequate specimen for diagnosis (Fig. 5) and even for special studies, such as electron microscopy and cytogenetics, if these are indicated. This technique may also be used in the operating room and has the advantage of minimizing subcutaneous hematoma and fascial dissection of hematoma, which are sometimes associated with an open biopsy.
When a core needle biopsy specimen is inadequate or non-diagnostic, an open biopsy is necessary. A frozen section to determine whether the biopsy specimen contains diagnostic tissue is an essential step whenever the biopsy is performed with the patient under general anesthesia.
Open excisional biopsy can be used to diagnose lesions that the surgeon is certain are benign. Lipomas, hemangiomas, and ganglions are often removed as the excisional biopsy specimen. This technique can also be used to treat very small lesions (less than 1.5 centimeters in diameter) of unknown type. Open excisional biopsy should not be used for indeterminate soft-tissue masses that are more than 1.5 centimeters in diameter, because excisional biopsy of a sarcoma results in operative margins that are either microscopically or grossly positive for malignant tumor cells. Such contaminated excisional biopsy tracks markedly compromise definitive treatment. Repeat excision therefore has to be far more extensive, involving more muscle, subcutaneous tissue, and skin than if the contaminated excisional biopsy had not been performed. Furthermore, sensory and motor nerves that have been contaminated by the excisional biopsy often have to be excised as well.
Open incisional biopsy is the most reliable method of obtaining sufficient tissue to establish the correct histological diagnosis and grade. From a technical standpoint, open biopsy is demanding and must be carefully planned. Several technical points must be emphasized.
1. The location and orientation of the biopsy incision must be planned so that the entire biopsy track can be excised if the lesion is malignant and operative resection is necessary (Fig. 6). Transverse incisions on the extremities should be avoided.
2. The incision should be as small as possible. When the mass is located in the subcutaneous tissue, the incision should parallel the direction of the muscle fibers below the mass. When the mass is located below the deep fascia, a direct incision that does not raise flaps should be placed in line with the underlying muscle fibers. If the mass is within or beneath muscle tissue, it is best to avoid intermuscular planes and to obtain tissue by intramuscular blunt dissection to avoid any spread of the tumor along the intermuscular planes. Care should be taken to avoid exposure of major nerves or vessels during the biopsy to prevent their contamination with tumor cells.
3. Meticulous hemostasis must be achieved to prevent the formation of a hematoma that might spread tumor cells into the adjacent subcutaneous tissue. The tissue from the lesion is best obtained under tourniquet control (with the limb exsanguinated by gravity rather than by wrapping the limb with an elastic or Esmarch bandage). After the tissue has been obtained, the tumor bed may be packed with a hemostatic agent and gauze, and the limb may be wrapped with an elastic bandage for compression. The tourniquet is then deflated, and the biopsy material is brought to the frozen-section laboratory.
4. The biopsy tissue must be handled carefully. Two biopsy receptacles should be used, with a small amount of representative tissue from the biopsy held in a second container for permanent sections. The frozen section is performed to ensure that a representative tissue specimen is available to the pathologist for diagnosis. If the frozen section suggests a lymphoma or small blue-cell tumor (such as Ewing sarcoma, primitive neuroectodermal tumor, or undifferentiated small-cell tumor), fresh tissue from the second container is used for special studies. Unless there is a definitive diagnosis on the basis of the frozen section, a specimen should be obtained for culture.
5. The wound must be carefully closed after hemostasis has been achieved. This may necessitate a period of direct compression with a hemostatic aid, such as oxidized cellulose, before the muscle and fascia are closed with interrupted sutures. The subcutaneous tissue and skin should be closed tightly with sutures to minimize the amount of skin and subcutaneous tissue that will have to be resected if the mass is found to be malignant. If there is any question as to the adequacy of hemostasis, a small drain should be brought out distally (within one centimeter) and in line with the incision.
6. A Robert Jones-type compression dressing should be used when the biopsy is performed on an extremity. The dressing should be layered in the following manner, in order from the skin: soft roll, bulky cotton, gauze wrap, and elastic wrap.
7. In a cost-conscious health-care environment, most patients who have only a biopsy are expected to go home on the same day as the procedure. However, if the surgeon believes that undue activity may create additional bleeding and subsequent spread of the hematoma, overnight bed rest in the hospital may be the most appropriate care for the patient.
Soft-tissue tumors are classified according to the direction of differentiation of the tumor cells. There are more than 200 different benign and seventy different malignant entities11 (Table I). The benign entities can be divided into the true neoplasms (extra-abdominal desmoid tumor and hemangioma) and reactive conditions (such as heterotopic ossification and nodular fasciitis).
Benign soft-tissue lesions can be staged according to the system of the Musculoskeletal Tumor Society8,9 (Table II). The system is very useful in that the plan for observation or operative treatment can be based on the stage of the lesion. Inactive (stage-1) lesions can be treated with observation only. Active (stage-2) lesions usually can be treated with a simple resection (an intralesional or so-called marginal margin, in which the line of dissection enters the reactive zone of the tumor), while aggressive (stage-3) lesions (lesions that are locally aggressive in that they invade or surround normal structures such as nerves, blood vessels, bone, or other structures) may need a wide operative margin in which the line of dissection removes the tumor with a cuff of normal tissue (Table III).
There are many common as well as rare soft-tissue lesions that may be encountered by the surgeon, and several large textbooks have addressed the presentation, histological features, and biological behavior of these lesions11. In the scope of this short lecture, only the common benign lesions—lipomas, ganglion cysts, subcutaneous and intramuscular hemangiomas, nodular and proliferative fasciitis, heterotopic ossification, and nerve-sheath tumors—can be introduced.
Lipomas
Proliferations of adipose tissue throughout the body are common. They are, in fact, the most common soft-tissue tumors of the musculoskeletal system. Enzinger and Weiss11 classified benign lipomatous tumors into five categories (Table IV).
Lipomas usually occur in adults and are more common with advancing age. Most are superficial and occur in the region of the back, shoulder, or neck11. Other common locations include the proximal aspect of the arm, the buttock, and the proximal aspect of the thigh. Lipomas arising below the level of the fascia are much less common, and they often attain a large size before they are brought to a physician's attention. Most lesions do not cause symptoms and grow slowly. Superficial lipomas usually have a doughy or cystic consistency11. Deep lipomas often feel firmer and may be difficult to distinguish from a sarcoma with palpation alone.
With a deep-seated lipoma, plain radiographs may show a radiolucent lesion (Fig. 7-A). The magnetic resonance image demonstrates signal characteristics that are identical to those of the surrounding adipose tissue (Fig. 7-B). Histologically, lipomas are composed of mature fat. At resection, a thin fibrous capsule is found surrounding the tumor. Simple excision (a marginal margin) is the treatment of choice, and recurrence is not common. Truly benign lipomas probably have no malignant potential.
There are four lipoma variants with which the surgeon should be familiar.
Angiolipoma: Angiolipoma occurs as a painful, subcutaneous nodule in young adults. The forearm is the most common site, followed by the trunk and the proximal aspect of the arm. Two-thirds of the lesions may be multiple. Hypercellular angiolipomas may be confused histologically with both Kaposi sarcoma and angiosarcoma11.
Spindle-cell lipoma: This presents as a painless, firm nodule, most commonly in the neck or shoulder, in men between the ages of forty-five and sixty-five years10,11. Histologically, the lesion contains both fat cells and well differentiated spindle cells.
Pleomorphic lipoma: Pleomorphic lipoma is a very uncommon lesion that presents in a similar manner to spindle-cell lipoma. In addition to the spindle cells and lipocytes, there are bizarre giant cells11,20. This lesion may be confused with a malignant mesenchymal tumor.
Intramuscular and intermuscular lipomas: These lipomas can attain a large size. They are most common in men and in the lower extremity. They tend to infiltrate muscle diffusely and may grow around peripheral nerves but not into them. When these lipomas are excised, great care is needed to avoid nerve injury in the forearm, where the lipomas may displace or surround peripheral nerves (Figs. 8-A and 8-B). These lesions may mimic sarcomas in both their presentation and their physical characteristics.
Large fatty tumors may pose a difficult diagnostic problem. Transverse imaging studies (either magnetic resonance or computed tomography scans) may show that the lesions are minimally heterogeneous. Benign lipomas may contain fibrous strands or even islands of bone. The transverse images are often interpreted as consistent with a large lipoma, with the caveat that the lesion could be a liposarcoma (Fig. 9). In this scenario, it is best to perform a small open biopsy of the lesion. Adipose tissue is not amenable to frozen-section analysis so only permanent sections are made. Examination of permanent sections usually results in one of three diagnoses: lipoma, atypical lipoma, or grade-I lipoma-like liposarcoma. It may be difficult to differentiate atypical lipoma from well differentiated liposarcoma12. Fortunately, both of these lesions have little risk of metastasis and both can be treated with a conservative operative resection (a marginal margin or, at most, a wide margin conserving normal structures).
Ganglion Cysts
Ganglion cysts are very common lesions. They usually occur at the wrist, where they are easily recognized. Outside of their typical location in an upper extremity, they may simulate more clinically aggressive lesions (Figs. 3, 10-A, and 10-B). Ganglion cysts may arise from the proximal tibiofibular joint and the joints about the ankle. At the knee, they may compress the common peroneal nerve, causing a neurological deficit. At the ankle, posterior tibial nerve compression may cause tarsal tunnel syndrome. Treatment is excision of the cyst. When possible, the stalk should be traced to its origin, although doing this is not always feasible. Although recurrence is common, the recurrence is usually smaller and most patients do not need a second procedure.
Popliteal cysts are a special category of ganglion cyst and frequently contain viscous fluid rich in hyaluronate that is indistinguishable from the fluid in more conventional ganglia found in subcutaneous sites. These cysts may become quite large and firm and are easily confused with a more ominous popliteal sarcoma. Examination of fluid aspirated with an 18-gauge needle reveals the contents of the mass, and if the aspirated material is indeterminate a magnetic resonance image clarifies the nature of the mass. The magnetic resonance image usually demonstrates communication with the knee joint and that the lesion contains fluid. Most symptomatic popliteal cysts are secondary to an intra-articular etiology (such as meniscal tears, arthritis, or osteoarthrosis), and treatment should be directed at the specific pathology.
Subcutaneous and Intramuscular Hemangiomas and Arteriovenous Malformations
The terminology applied to vascular-based growth presenting as a soft-tissue mass has been primarily descriptive in nature, with a variety of adjectives applied to the term hemangioma, such as juvenile, capillary, cavernous, and cirsoid. More recently, the term hemangioma has been reserved for vascular abnormalities that show endothelial hyperplasia and increased numbers of mast cells, while all other vascular abnormalities with normal endothelial characteristics but increased flow and increased numbers and types of vessels have been designated arteriovenous malformations13,24. Some authors have suggested "symptomatic vascular malformation" as a generic term to allow further delineation without confusion24.
Hemangiomas are common and may occur in either the superficial (cutaneous or subcutaneous) or deep tissues. Patients who have a superficial hemangioma usually present with a visible and palpable mass. Unlike patients who have a deep, well defined intramuscular symptomatic vascular malformation, patients who have a deep intra-arterial hemangioma often have a diffuse, aching sensation after prolonged standing or activity (Fig. 2). On physical examination, the mass may be difficult to detect with the patient supine, as the lesion is not filled with blood. The patient should be asked to stand for two or three minutes and should then be examined a second time, as the affected segment often takes on a full or distended characteristic.
Plain radiographs may show phleboliths or periosteal thickening of the adjacent bone (Fig. 11-A). Magnetic resonance images are characteristic, demonstrating numerous small blood vessels and variable amounts of fat4,5 (Fig. 11-B). Histologically, these lesions may be of the small-vessel, cavernous, or mixed type and are classified as noted previously on the basis of endothelial cell-lining characteristics.
Treatment is difficult, and non-operative treatment should be attempted first. The use of non-steroidal anti-inflammatory medications and surgical support stockings provides relief for some patients. Embolization is also an option if specific large feeder vessels can be localized; however, most patients are not candidates for this procedure. Resection of muscle groups or subcutaneous tissues can be performed but is fraught with problems. In superficial lesions, dissection of the hemangioma from the overlying skin can be difficult and can result in cutaneous devascularization. A soft-tissue expander implanted in the adjacent subcutaneous tissue for three to six weeks before excision of the hemangioma may facilitate closure. The lesion can then be resected, and the expanded tissue can be shifted to fill the defect3,19.
Intramuscular hemangiomas pose a more difficult therapeutic problem. When the symptomatic vascular malformation is small and characteristic of a hemangioma, it may be treated successfully with local excision (Fig. 12). However, when the process diffusely involves the entire muscle unit (Fig. 2), the disability created by the loss of the muscle has to be weighed against the morbidity of the condition and other possible treatments.
Tumor-Like Soft-Tissue Lesions
Two inflammatory conditions of fascia, nodular fasciitis and proliferative fasciitis, present as firm, enlarging soft-tissue masses. They must be distinguished from malignant tumors, but differentiation on histological grounds is often difficult, particularly on frozen section alone. Careful consultation between the surgeon and the pathologist is a prerequisite for arriving at the correct diagnosis, and often with these patients it is wise to obtain an outside confirmatory pathology consultation.
Nodular fasciitis: This lesion is a non-neoplastic proliferation of fibroblasts that most commonly occurs in young adults11. The lesion is characterized by rapid growth, and the patient may or may not have pain over the mass (Fig. 13). The most common location is the upper extremities. There are three types of nodular fasciitis: subcutaneous, intramuscular, and fascial11. Histologically, the lesion can be confused with a sarcoma because of its hypercellularity and mitotic activity. Excision with a marginal margin is all that is necessary for treatment, and recurrence is uncommon.
Proliferative fasciitis: Proliferative fasciitis is a benign, non-neoplastic lesion that is composed of immature fibroblast-like spindle cells, numerous basophilic giant cells, and occasional mitotic figures11. The lesion occurs in older adults (forty to seventy years old), and the forearm and thigh are the most common locations11. Patients present with a firm, subcutaneous nodule. As in nodular fasciitis, this lesion can be confused with a sarcoma. Treatment is excision with a marginal margin, and local recurrence is uncommon.
Heterotopic Ossification (Myositis Ossificans)
Heterotopic ossification most commonly occurs following trauma to the musculoskeletal system1,11. Patients usually present with swelling, pain, and a decreased range of motion. More than one-half of the patients have a history of a single injury or of multiple traumatic events. In some patients, despite extensive queries, no history of trauma is discovered. The most common locations include the thigh (the quadriceps muscle), the arm (the brachialis muscle), the shoulder (the deltoid and scapular muscles), and the hand11.
Initially, radiographs may show only faint, irregular, floccular radiodensities (sometimes called the dotted-veil pattern)11 (Figs. 14-A, 14-B, 14-C, 14-D through 14-E). As the lesion matures, the radiographic appearance changes to that of bone formation, characteristically beginning at the periphery of the lesion. The center of the lesion remains radiolucent, a characteristic that can be demonstrated well by computed tomography. In most patients, the lesion is not attached to the underlying bone, but it can be attached if it lies near the bone and the original injury induced an adjacent periosteal reaction. Serial radiographic studies done over a period of years will show the volume of heterotopic bone to decrease gradually. Treatment is aimed at restoring function. Initially, patients are managed with rest and anti-inflammatory agents. Gentle physical therapy is instituted when local heat, edema, and pain subside. Isometric muscle-strengthening and gentle, active assisted range-of-motion exercises within the limits of pain are progressively increased until full functional recovery. Manipulation should be avoided. Because the diagnosis can be established with an appropriate history and imaging studies, an operation is seldom necessary.
Benign Nerve-Sheath Tumors
Neurilemoma (Benign Schwannoma)
Neurilemoma is a common nerve-sheath tumor that occurs in adults who are twenty to fifty years old. The tumor typically involves the flexor surfaces of both the upper and lower extremities11. The mass is usually painless and grows very slowly. Neurological symptoms are uncommon. Patients may report that the swelling has been present for years and that the tumor increases and decreases in size. Changes in size are usually related to cystic change within the lesion.
Physical examination usually shows a painless mass that is mobile in all planes except the longitudinal direction of the nerve. Magnetic resonance scanning shows an eccentric mass originating from a peripheral nerve (Figs. 15-A and 15-B). Local resection can be accomplished by defining the plane between the tumor and the peripheral nerve. Once this plane is developed, the tumor can be dissected free of the nerve.
Histologically, the lesion contains two components: a highly ordered cellular component (Antoni A) and an loose myxoid component (Antoni B)11. When the lesion is predominantly cellular (cellular neurilemoma), it can be mistaken for a sarcoma.
Neurofibroma
Neurofibromas may be solitary or multiple. By definition, patients who have a solitary neurofibroma do not have von Recklinghausen disease11. Most neurofibromas are very superficial, lying in the dermis or subcutaneous tissue. Most patients present with painless nodules. Unlike schwannomas, which grow eccentrically from the nerve, neurofibromas grow from the center of the nerve and cause fusiform expansion. Histologically, neurofibromas contain variable amounts of cellular elements, mucin, and collagen11. Symptomatic neurofibromas may be excised when they do not involve major peripheral nerves.
Patients who have neurofibromatosis (von Recklinghausen disease) have multiple neurofibromas, café au lait spots, and skeletal abnormalities. The neurofibromas usually grow slowly. In these patients, a rapid increase in growth along with pain should alert the clinician to the possibility of malignant change within a neurofibroma.
Soft-tissue masses are common. The clinician must develop a systematic approach with regard to taking a careful history, performing a thorough physical examination, and ordering appropriate imaging studies. Plain radiographs are the most useful modality to determine whether the mass is arising in the soft tissues or in bone. Magnetic resonance imaging gives the best resolution both to characterize the lesion and to define the anatomical features. The biopsy must be planned carefully to avoid complications. Soft-tissue lesions should be reviewed closely by an experienced musculoskeletal pathologist. Treatment is based on the biological activity of the particular lesion. A careful, coordinated evaluation, involving the physician, radiologist, and pathologist, is necessary to avoid incorrect diagnoses and inappropriate treatment.
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