Soft tissue tumors may often be overlooked or mistaken as “simple lesions.” For example, ganglion cysts occur so frequently in the foot and ankle that it has often led to the careless assumption that every asymptomatic, soft, movable mass represents a benign lesion. Unfortunately, this lackadaisical confidence can lead to misdiagnosis and disaster in certain situations. Although rare, some “simple lesions” may actually represent a malignant process that goes undiagnosed until skeletal metastasis occurs or amputation is required. This tragedy could potentially lead to malpractice litigation for negligent care. What To Look For In The Initial Presentation Enzinger and Weiss defined soft tissue tumors as “non-epithelial extraskeletal tissue of the body exclusive of the reticuloendothelial system, glia and supporting tissue of various mesenchymal organs.”1 In light of that definition, soft tissue tumors of the foot and ankle region are relatively common when compared to their osseous counterparts and are more often benign than malignant.2 When a patient comes in with a soft tissue tumor, the first step is to determine whether the lesion is benign or malignant. These patients will initially present with a “bump” on the foot with some report of pain in shoegear or a limp during ambulation. Be aware that most soft tissue neoplasms in the foot and ankle present earlier in their course than tumors at other sites in the body because of the relatively thin soft tissues covering these areas.3 For example, small masses are usually easily palpable in the foot and ankle regions. Dorsal neoplasms often produce symptoms because of pressure from shoegear while plantar lesions are typically aggravated by weightbearing and ambulation forces. Be sure to emphasize a careful history and thorough documentation to determine the duration of symptoms, rate of growth, associated pain, history of trauma or infection. A family history is also essential. Common clinical symptoms, such as pain, discomfort, tenderness and localized swelling, may be secondary to mechanical obstruction of tightly bound gliding mechanisms of muscles, tendons and ligaments that encompass the foot and ankle areas. However, not all soft tissue neoplasms are painful or small. Statements such as “benign lesions are painless” and “malignant lesions are painful” are grossly inaccurate. Likewise, size is not a predictor of malignancy. A large tumor had to start as a small lesion at one point.4 Fortunately, as stated above, soft tissue tumors of the foot and ankle are much more likely to be benign than their malignant counterparts, soft tissue sarcomas. A Helpful Primer In Recognizing Ganglion Cysts And Lipomas Common benign soft tissue tumors one might see in the foot and ankle include ganglion cysts, lipomas, plantar fibromatosis (Ledder hose’s syndrome), hemangiomas and neurilemoma (schwannoma). As far as specific clinical chacteristics go … • Ganglion cysts are the most common soft tissue tumors in the foot and ankle. They are usually painless lesions of varying size that tend to occur in patients between the ages of 20 and 40. Female patients are three times more likely to develop these cysts. Aspiration with a large-bore, 18-gauge needle is diagnostic. You’ll note a clear, yellow and viscous fluid. Ganglionic fluid is the product of mucoid degeneration in an area of the joint capsule or tendon sheath. Ganglia may remain stationary, increase in size or spontaneously rupture and disappear. While ganglion cysts can occur at any location in the foot and ankle, they commonly arise from the dorsal surface and are in close opposition to tendons or joints. • Lipomas may occur in the soft tissue, muscle, tendon sheaths or bone. The mass is soft, non-tender, mobile and usually asymptomatic unless it compresses neural structures. Most lipomas of the foot are slow growing, located in the subcutaneous tissue and are usually solitary. You’ll usually see these lesions along the anteriolateral aspect of the ankle, but they may occur anywhere in the foot and ankle. Lipomas frequently occur in obese, post-menopausal women and are also common among patients who have hypercholesterolemia. What You Should Know About Plantar Fibromatosis • Plantar fibromatosis usually presents as a solitary lesion or multiple nodules, often occurring along the medial and central band of the plantar fascia. These lesions are typically unilateral, are firm and fixed to the plantar fascia. When patients are weightbearing, the lesions may produce discomfort due to the irregular contour of the plantar surface in the arch of the foot. However, most lesions are asymptomatic. These lesions usually have slow growth that stops once they reach a size of approximately 3 cm. Local adherence to the overlying skin is a common characteristic. Nodules consist of a hyperplasia of fibroblasts embedded within the plantar aponeurosis. It occurs more often in adolescents and young adults. Males are twice as likely to develop these lesions. Older patients may have associated palmer (Dupuytren’s disease) contracture of the hands or penile (Peyronie’s disease) fibromatosis. Certain systemic conditions (epilepsy, alcoholism, hypothyroidism and diabetes mellitus) are associated with a higher incidence. What About Hemangiomas And Neurilemomas? • Hemangiomas are benign vascular tumors that are believed to represent hamartomatous malformations of normal vascular tissues or benign neoplasms. Most are soft, compressible and subcutaneous in location. Tumors can be of the cavernous, capillary or mixed type with the port-wine capillary hemangiomas being most common in the foot. Hemangiomas generally arise during childhood and adolescence. When these tumors are superficial, you’ll notice a bluish discoloration associated with a soft, doughy mass. More extensive lesions may have associated, localized gigantism of adjacent bone and soft tissue. One may also see hemangiomas in conjunction with dyschondroplasia, also known as Maffucci’s syndrome. • Neurilemoma is a benign tumor of nerve sheath origin (Schwann cell) with a peak incidence in the fourth and fifth decades of life. There is no predilection to either gender. The tumor is usually solitary, less than 2 cm, well-encapsulated and on the surface of a peripheral nerve. Patients will present with a painful nodule associated with a Tinel’s sign in the distribution of the affected nerve. Essential Diagnostic Insights During the physical examination for soft tissue tumors, you should note whether the lesion is fixed or movable with reference to skin, tendons or bone. It’s essential to document your assessment of the tumor location, size, depth, consistency, skin changes, demarcation, neurovascular status and joint involvement.5 However, keep in mind that a diagnosis based on palpation alone is notoriously unreliable. For example, the physical examination of a ganglion cyst may be soft, firm or hard.6 Various clinical tests, such as transillumination and auscultation, can provide valuable information in the initial evaluation of fluid-containing and vascular lesions, respectively. Standard radiographs are an extremely useful imaging modality for osseous neoplasms. However, they are much less informative when dealing with soft tissue lesions. In spite of this fact, radiographs should be your first imaging option. An increased soft tissue density and volume, and the presence of soft tissue calcification are important diagnostic considerations in soft tissue lesions. Obtaining plain radiographs allows you to see concomitant osseous involvement such as bony destruction, erosion, periosteal reaction or remodeling. For example, pigmented villonodular synovitis frequently causes bony juxtacortical bony erosions that one can easily appreciate on plain films.8 Ultrasonography is helpful in differentiating between solid and cystic (fluid-filled) lesions. You will find that fluid-filled lesions present as an anechoic mass or homogeneously black on ultrasound whereas solid lesions typically appear as hypoechoic mass. Also keep in mind that purely cystic masses are not likely to be malignant.9 Employing ultrasonography can also help you determine the size and depth of the neoplasm. Color Doppler ultrasonography has proven useful in demonstrating the vascular supply of certain vascular tumors. This eliminates certain lesions from a differential diagnosis. Additionally, you can use this modality to monitor the location of a percutaneous needle biopsy if neurovascular structures are in proximity. Unfortunately, despite its value as a rapid and inexpensive diagnostic medium, ultrasound still remains an underutilized modality in evaluating soft tissue tumors.10 Radionuclide bone scans provide information regarding the intensity of uptake in a specific lesion. Soft tissue lesions that show increased uptake may be benign or malignant. However, lesions that show no uptake on scanning are invariably benign. If you have a strong suspicion of skeletal metastasis, it is standard practice to obtain a technetium 99m (99mTc) bone scan.11 Angiography may provide information regarding the proximity of lesions to neurovascular bundles. However, its role has been limited by the advent of computed tomography (CT) and magnetic resonance imaging (MRI). CT can provide valuable information regarding calcification or ossification within the lesion and whether the lesion is penetrating into osseous structures. However, for the vast majority of soft tissue tumors, MRI has become the imaging method of choice.12 Not only does the MRI provide superior soft tissue contrast and multiplanar images, it eliminates ionizing radiation and defines marrow involvement if osseous extension is evident. A Few Thoughts About New Advances In Diagnostic Techniques Recently, two new imaging techniques have evolved and show promise in identifying soft tissue tumors. Dynamic contrast-enhanced MRI (DCEMRI) uses contrast material (gadolinium or gadopenteate dimeglumine) to provide excellent evaluation of anatomic localization in pre-operative surgical planning of soft tissue tumors.13 Positron emission tomography (PET) uses 2-fluoro-2-deoxy-D-glucose (FDG) molecule to enter tumor cells using glucose transporters.14, 15 These sophisticated scanning tests are primarily used to determine the stage of the tumor, response to therapy and monitor recurrence in difficult cases. Despite the continuing advances in these diagnostic imaging studies, keep in mind that sometimes these techniques do not adequately distinguish between benign and malignant disease processes. When it comes to establishing whether the soft tissue tumor is benign or malignant, one should definitely perform a histological examination of the tumor.16 Obtaining a biopsy is the critical step in determining the nature of the tumor. Nevertheless, it is recommended that you pursue all imaging and laboratory studies prior to the biopsy. Key Considerations In Biopsy Planning Although a biopsy is considered simple practice, one should not underestimate its significance as it is an important surgical procedure. While the biopsy is often used as a diagnostic tool, it is also used as part of the staging sequence for malignant lesions. While performing a biopsy is not technically demanding, the planning for it is.17 Also be aware that a “simple biopsy” is not without inherent risks and may result in tumor implantation and/or extension if the lesion turns out to be malignant.18 For that reason, all biopsies carry potential risk to a patient’s limb or life. The lesions at greatest risk are those in which a malignant diagnosis was not considered in the initial differential diagnosis. An important dilemma arises, “When do you get a biopsy or simply just observe a lesion?” In order to answer this vital question, you must rely on clinical judgment, appropriate imaging techniques and laboratory studies in combination with the patient history and physical findings. The next complicated decision is choosing between a closed biopsy (needle aspiration or a percutaneous core needle) or an open biopsy (excisional, incisional or wide excision) method.19 Technique is crucial and serious complications may result from an improperly or poorly executed biopsy. Consequently, all biopsies must be carefully planned and well executed to minimize possible complications such as poor incision placement, sampling error, inadequate tissue resection and soft tissue contamination.18 It is essential to consider the surgical margins that may be needed for definitive treatment before the biopsy so one may make the incisions in a position to be completely excised as part of the specimen at final resection. Poorly planned or executed biopsies can result in misdiagnosis and a delay in treatment.20 Planning for a biopsy is dependent on your knowledge of the origin of soft tissue tumors (see “Reviewing The Classification Of Soft Tissue Lesions”) and your ability to develop a differential diagnosis. A differential diagnosis guides the relative indications for a biopsy and the various possible definitive treatments of the tumors being considered. You must always consider a lesion to be malignant so that appropriate needle tracts or skin incisions from the biopsy do not interfere with any possible future reconstruction that may become necessary. A Closer Look At Open Biopsies For the vast majority of soft tissue tumors in the foot and ankle, open biopsy is the preferred method. However, each technique carries its own potential advantages and disadvantages. An excisional biopsy is basically a technique of removing the entire lesion at the time of biopsy. One should perform an excisional biopsy for lesions that are assumed to be benign or are small enough that one can remove them in toto with a small surrounding section of normal tissue. In the foot and ankle, this procedure is reserved for lesions less than 3 cm. When using this procedure, you can remove the entire lesion, avoid potential seeding and increase diagnostic accuracy due to the larger sample size. The excisional biopsy is an adequate treatment for small benign or low-grade malignant lesions. An incisional biopsy involves directly cutting into the lesion to remove a sample without excising the entire lesion. It is preferred for larger lesions (greater than 3 cm) or presumptive malignant lesions that would require undue sacrifice of normal tissue to achieve a wide margin with the biopsy. A disadvantage is potential contamination of tumor cells.19 A primary wide excision biopsy involves removing the entire lesion while excising a large portion of normal, healthy tissue. The surrounding rim of the tumor is attached and left undisturbed with the resection. Disadvantages of this biopsy technique often include major functional and cosmetic defects. This is the most aggressive biopsy technique so use it with caution since the patient may be better served with a functional amputation and fitted prosthesis. You would only use this technique when you highly suspect malignancy and when there is a great risk of contaminating major neurovascular structures.4 Reviewing The Pros And Cons Of Closed Biopsies Needle aspiration is a beneficial diagnostic tool often used to differentiate fluid-filled (cystic) lesions from solid lesions. If you suspect a solid, potentially malignant lesion instead of a benign, fluid-filled, cystic lesion, attempted aspiration for confirmation is strongly recommended.21 This requires a large-bore, 18-guage needle. When lesions do not yield fluid, you should consider them to be potentially malignant in nature until proven otherwise. Aspiration causes no morbidity if the lesion proves to be a ganglion cyst. If you find the lesion is solid, you may treat it as a needle tract site that you can later remove during a biopsy. Cautious aspiration of a suspected ganglion is an easy and acceptable method of verifying a supposed diagnosis. However, if you cannot obtain typical ganglion fluid, do not assume the fluid was too thick to aspirate.6 Give serious consideration to the possibility of the lesion being a solid tumor and of greater consequence. While percutaneous core needle biopsy is commonly used for large soft tissue masses, it is not routinely employed in the foot and ankle areas. Most core needle biopsies are reserved for lesions with an obvious diagnosis from the staging studies.22 Disadvantages of core needle biopsy techniques include inadvertent extension of the lesion by the depth of needle penetration or subsequent hematoma formation. Also keep in mind that the quantity of specimens you obtain may not be sufficient for adequate diagnosis.4 What You Should Know About Pre-Operative Staging Pre-operative staging of lesions provides a rationale for definitive surgical treatment and long-term prognosis.4 Staging combines radiographic, histologic and clinical data to categorize tumors. Enneking has devised both benign and malignant staging systems.19, 23 Benign soft tissue tumors are classified as follows into three stages based on latent, active and local aggressive growth.24 Stage 1. Lesions are latent or inactive (static) and usually have no clinical symptoms. Examples include lipoma, ganglionic cyst and fibroma. Stage 2. Lesions are actively growing and are associated with clinical symptoms. Examples include xanthoma, glomus tumor, neurilemoma and neurofibroma. Stage 3. Lesions are locally aggressive, histologically immature and show progressive growth that is not limited by normal anatomic boundaries. Examples include hemangioma, plantar fibromatosis and PVNS. Soft tissue sarcomas (malignant) are graded into low-grade (Stage I) and high-grade (Stage II) tumors based on histologic appearance coupled with diagnostic imaging characteristic and anatomical location.23 Sarcomas with the presence of distant metastasis are considered Stage III tumors. If you suspect a malignant sarcoma, a consultation or referral with a musculoskeletal oncologist is strongly recommended. The Enneking Staging for Malignant Soft Tissue Sarcomas is as follows: Stage IA is a low-grade tumor at the intercompartmental site with no metastasis. Stage IB is a low-grade tumor at the extracompartmental site with no metastasis. Stage IIA is a high-grade tumor at the intracompartmental site with no metastasis. Stage IIB is a high-grade tumor at the extracompartmental site with no metastasis. Stage III is a tumor at either anatomical site with metastasis. A Review Of Indications For Surgical Margins The essential treatment for both benign and malignant soft tissue tumors is surgical resection. Clinical success rates are directly related to the adequacy of the surgical margins. Intralesional margins can be used to remove the lesion from within the reactive pseudocapsule but this approach is rarely utilized. Marginal surgical margins are used to remove the lesion by dissection around the outside of the pseudocapsule. This approach is recommended for stage I and II lesions, but be aware that it may leave microscopic disease behind. Wide surgical margins are employed to remove the lesion (and biopsy tract site) with a modest amount of normal tissue so you don’t expose the reactive pseudocapsule. This approach is for stage III lesions and low-grade malignant lesions. Radical margins are used to remove the entire anatomic compartment(s) that contain the lesion. This may include amputation and is recommended for high-grade malignant lesions. Your choice of surgical margin is determined by the type and stage of the lesion.1, 4, 19 Additionally, surgical resection is also determined by the anatomic location and the estimated disability from the resection.16, 19 Recommendations For Surgical Correction When it comes to most benign stage I and II soft tissue lesions, you can generally treat them with marginal excision as long as you can achieve this without sacrificing vital structures. Benign stage III and malignant stage I (low-grade sarcoma) soft tissue lesions typically require wide margins for definitive treatment. However, be aware that if there is involvement of adjacent tendons, neurovascular structures and bone, wide excision may sacrifice too much tissue to leave a functional foot and ankle.4, 25 Given the disability that would result from achieving an appropriate surgical margin, an amputation is preferred in this instance as it will achieve the desired margin and also offers the best method of reconstruction and rehabilitation.19, 26, 27 Most malignant stage II (high-grade sarcoma) lesions and all malignant stage III lesions requiring margins usually require radical resection or amputation as definitive treatment. Occasionally, malignant sarcomas may benefit from adjunct radiation or chemotherapy. For this reason, making a referral to a musculoskeletal oncologist is highly recommended. Dr. Walter is the Chairman and a Professor in the Department of Podiatric Orthopedics and Biomechanics at the Temple University School of Podiatric Medicine in Philadelphia. He is a Fellow of the American College of Foot and Ankle Surgeons and the American College of Foot And Ankle Orthopedics and Medicine. Dr. Goss is an Adjunct Clinical Instructor in the Department of Podiatric Orthopedics and Biomechanics at the Temple University School of Podiatric Medicine in Philadelphia. He is the Director of Podiatric Surgical Residency at Tenet Parkview Hospital in Philadelphia, and has a private practice, Philadelphia Foot & Ankle, PC, in Bala Cynwyd, Pa. Dr. Goss is a Fellow of the American College of Foot and Ankle Surgeons and the American College of Foot And Ankle Orthopedics and Medicine.
References 1. Enzinger FM, Weiss SW: Soft-Tissue Tumors. St. Louis: Mosby, 1995. Johnson MR. Epidemiology of soft-tissue and bone tumors of the foot. Clin Pod Med Surg 10(4):581, 1993. 2. Johnson MR. Epidemiology of soft tissue and bone tumors of the foot. Clin Pod Med Surg 10(4): 581, 1993. 3. Seale KS, et al: Soft tissue tumors of the foot and ankle. Foot Ankle 9:19, 1988. 4. Walling AK, Gasser SI: Soft-tissue and bone tumors about the foot and ankle. Clin Sports Med 13:909, 1994. 5. Potter GK. Evaluation of a patient with a pedal neoplasm. Clin Pod Med Surg 10(4):609, 1993. 6. Pontious J, Good J, Maxiam SH: Ganglions of the foot and ankle: A retrospective analysis of 63 procedures. JAPMA 89(4):163, 1999. 7. Mykre-Jenson O: A consecutive 7-year series of 1,331 benign soft-tissue tumors: Clinicopathologic data and comparison with sarcomas. Acta Orthop Scand 52:287, 1981. 8. Walter JH, Galitz J, Robertson DW: Pigmented villonodular synovitis pedal manifestations. JAPMA 84:574, 1994. 9. Levey DS, Park YH, Sartoris DJ, Resnick D: Imaging methods for assessment of pedal soft-tissue neoplasms. Clin Pod Med Surg 10(4):617, 1993. 10. Fornage BD: Soft tissue masses: The underutilization of sonography. Semin Musculoskel Radiol 3:115-133, 1999. 11. Nishiyama Y, Yamamoto Y, Toyama Y, Satoh K, Ohkawa M, Tanabe M: Diagnostic value of T1-201 and three-phase bone scintigraphy for bone and soft tissue tumors. Clin Nucl Med 25:200-205, 2000. 12. Kransdorf MJ, Jelinek, JS, Moser RP: Imaging of soft tissue tumors. Radiol Clin North Am 31:359-372, 1993. 13. Shapeero LG, Vanel D, Verstragte KL, et al: Dynamic contrast-enhanced MR imaging for soft tissue sarcomas. Semin Musculoskel Radiol 3:101-113, 1999. 14. Schwarzbach MH, Dimitrakopoulou-Strauss A, Willeke F, et al: Clinical value of [18-F] fluorodeoxyglucose positron emission tomography imaging in soft tissue sarcomas 231:380-386, 2000. 15. Eary JF, Conrad, EU, Brucker JD, et al: Quantitative [F-18] fluorodeoxyglucose positron emission tomography in pre-treatment and grading of sarcoma. Clin Canc Res 4: 1215-1220, 1998. 16. Gibbs CP, Peabody TD, Simon MA: Mini-symposium: Soft tissue tumors of the musculoskeletal system: classification, clinical features, preoperative assessment, and staging of soft tissue tumors. Current Orthopaedics 11:75, 1997. 17. Peabody TD, Gibbs CP, Simon MA: Evaluation and staging of musculoskeletal neoplasms. J Bone Joint Surg 80A:1204, 1998. 18. Mankin HJ, Mankin CJ, Simon MA: The hazards of biopsy, revisited: Members of the Musculoskeletal Tumor Society. J Bone Joint Surg Am 78:656-663, 1996. 19. Enneking WF: Musculoskeletal tumor surgery, New York, Churchill Livingstone, 1983. 20. Giulano AE, Eilber FR: The rationale for planned reoperation after unplanned total excision of soft tissue sarcomas. J Clin Oncol 3:1344, 1985. 21. Akerman M, Rydholm A, Persson BM: Aspiration cytology and soft tissue tumors: The 10-year experience at an Orthopaedic Oncology Center. Acta Orthop Scand 56:407, 1985. 22. Laredo JD: Percutaneous biopsy of primary soft tissue tumors. Semin Musculoskel Radiol 3:139-144, 1999. 23. Enneking WF, Spanier SS, Goodman MA. A system for the surgical staging of musculoskeletal sarcomas. Clin Orthop 153:106, 1980. 24. American Joint Committee on Cancer - Soft-Tissues. In: Fleming ID, Cooper JS, Hensen DE, et al., eds. American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 5th ed. Philadelphia: Lippincott-Raven, 149, 1997. 25. Choll LB, Malawer MM: Analysis of surgical treatment of 33 foot and ankle tumors. Foot Ankle 15:175, 1994. 26. Harrelson JM: Tumors of the foot. In Jahss MH, editor: Disorders of the foot and ankle, ed 2, Philadelphia, 1991, WB Saunders. 27. Hattrup SJ: Metastatic tumors of the foot and ankle. Foot Ankle 8:23, 1988.