Soft tissue sarcomas are a rare, heterogeneous group of malignancies that should be included in the differential diagnosis for any patient presenting with a soft tissue mass. This article reviews strategies for differentiating between benign and malignant soft tissue masses. Epidemiology, appropriate workup, and treatment of soft tissue sarcomas are reviewed.
Key points
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Soft tissue sarcoma should be on the differential diagnosis for any patient presenting with a soft tissue mass.
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Soft tissue sarcomas do not always display aggressive clinical behavior. Although the classic description is an enlarging, subfascial mass greater than 5 cm, some sarcomas are superficial and have a very indolent growth rate.
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Patients with suspected soft tissue sarcomas should be referred to a specialty center with a multidisciplinary sarcoma team before biopsy is performed. Although less invasive than open biopsies, even percutaneous biopsies can complicate potential resections. Furthermore, some biopsies performed before referral are unnecessary, and can lead to unnecessary patient anxiety.
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Patients who undergo unplanned resection of a soft tissue sarcoma should be referred to a specialty center for consideration of reexcision and radiation therapy.
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Delays in diagnosis and unplanned resections have been associated with worse patient outcomes.
Introduction
Soft tissue masses are commonly encountered in general orthopedic clinics. Differentiation between benign and malignant soft tissue masses is challenging. When a systematic approach is applied to the workup for soft tissue masses, however, the chances of a delay in diagnosis or an unplanned resection are minimized. Early referral to a tumor center with an experienced multidisciplinary team for further workup of masses suspicious for soft tissue sarcoma leads to better patient outcomes.
There are approximately 11,000 new cases of soft tissue sarcoma diagnosed each year, which account for approximately 1% of all cancers diagnosed in the United States. Soft tissue sarcomas represent a heterogeneous group of malignancies. The many subtypes of soft tissue sarcomas share a common mesenchymal tissue of origin. Despite this similarity, soft tissue sarcomas exhibit a wide range of histologic findings and clinical behavior. This heterogeneity leads to diagnostic and therapeutic challenges. Soft tissue sarcomas develop in patients of all ages with a slight male predominance. These tumors are most likely to occur in the lower extremity, followed by the upper extremities and trunk.
Introduction
Soft tissue masses are commonly encountered in general orthopedic clinics. Differentiation between benign and malignant soft tissue masses is challenging. When a systematic approach is applied to the workup for soft tissue masses, however, the chances of a delay in diagnosis or an unplanned resection are minimized. Early referral to a tumor center with an experienced multidisciplinary team for further workup of masses suspicious for soft tissue sarcoma leads to better patient outcomes.
There are approximately 11,000 new cases of soft tissue sarcoma diagnosed each year, which account for approximately 1% of all cancers diagnosed in the United States. Soft tissue sarcomas represent a heterogeneous group of malignancies. The many subtypes of soft tissue sarcomas share a common mesenchymal tissue of origin. Despite this similarity, soft tissue sarcomas exhibit a wide range of histologic findings and clinical behavior. This heterogeneity leads to diagnostic and therapeutic challenges. Soft tissue sarcomas develop in patients of all ages with a slight male predominance. These tumors are most likely to occur in the lower extremity, followed by the upper extremities and trunk.
Clinical presentation and evaluation
The clinical presentation of a soft tissue sarcoma is nonspecific and similar to that of many benign masses. Despite the frequently aggressive histologic nature and propensity for metastasis of this heterogeneous class of tumors, soft tissue sarcomas are often painless. When evaluating a patient with a soft tissue mass, a thorough history should be obtained that specifically notes the chronicity of the mass, changes in size or appearance, and the nature of the discovery of the mass. Constitutional symptoms are uncommon in patients with soft tissue sarcomas and thus a patient who appears healthy may indeed be harboring a soft tissue sarcoma. Several common diagnoses and their salient clinical features are described in Table 1 . The key to avoiding unplanned resections and misdiagnoses is for the clinician to assume that all soft tissues are potentially malignant.
| Diagnosis | History | Physical Examination | Radiograph | MRI | Other Notes |
|---|---|---|---|---|---|
| Abscess | Painful, rapid onset History of prior abscess +/− fever | Erythema, warmth, tenderness, fluctuance | Nonspecific mass effect | Rim enhancement with administration of contrast May be loculated | Elevated inflammatory markers |
| Aneurysm | History of trauma common May be congenital More common in elderly patients | Compressible, pulsatile Popliteal fossa common site | +/− calcification of portions of vessel wall | Vessel enlarged in area of clinical concern Given vascular nature of this lesion, it enhances with contrast | Pseudoaneurysms more common than true aneurysms |
| Ganglion cyst | Mass may fluctuate in size Wrist common location | Mobile, tense but compressible May arise from capsules, tendon sheaths Transilluminates | Nonspecific mass effect | Rim-enhancing homogeneous lesion with intralesional signal intensity similar to that of water (dark on T1, bright on T2) | Classic presentation is dorsal wrist ganglion |
| Hemangioma | Dependent or activity-related fluctuations in size Female predominance | Soft, compressible Vascular ectasia may be present | Phleboliths (see Fig. 3 ) | Enhancing heterogeneous mass with characteristic serpentine appearance related to multiple vessels | Most common soft tissue mass in children |
| Hematoma | History of trauma Bleeding diathesis | Ecchymosis, warmth | Nonspecific mass effect | Nonenhancing heterogeneous mass Areas of high T1 signal represent ongoing hemorrhage | Soft tissue sarcomas may be erroneously diagnosed as hematomas on ultrasound and MRI (see Fig. 9 ) |
| Lipoma | Usually painless mass without rapid changes in size May cause symptoms from compression of neurovascular structures | Soft, mobile, nontender | Area of increased radiolucency within a more radiodense area of skeletal muscle (see Fig. 4 ) | Isointense with fat on all sequences ( Fig. 1 ) Presence of fibrous degeneration, broad septations, or nodularity merit further evaluation with tissue sampling ( Fig. 2 ) | Most common superficial mass in adults |
| Myositis ossificans | History of trauma Most common age in 20s Initially painful | Tenderness early in the course Quads and brachialis most common sites | Well-defined calcification around periphery of mass (see Fig. 5 ) | Decreased signal around periphery of lesion consistent with peripheral calcification pattern | CT more helpful for evaluating peripheral calcification of lesion |
| Neurofibroma | Most common in patients with neurofibromatosis +/− pain | Firm, +/− tenderness Positive Tinel sign at the mass Mobility in the transverse plane but not in the longitudinal plane | Nonspecific mass effect | Enhancing heterogeneous lesion Target sign on T2 sequencing described as circumferential area of high signal (myxoid tissue) around a center of low signal (nerve fibers) | Serial MRI may be used to monitor for degeneration to malignancy |
| Synovial cyst (Baker cyst) | Mass located in popliteal fossa +/− pain Fluctuates in size Associated with intraarticular pathology | Popliteal fossa Tense, compressible Clinically similar to ganglion | Nonspecific mass effect +/− Calcifications | Nonenhancing homogeneous lesion with signal intensity similar to that of water (dark on T1, bright on T2) | Communicates with joint Rupture of Baker cyst can lead to local pain |
A detailed medical history should be attained, taking specific note of any history of prior masses or cancer. Lymphoma, multiple myeloma, and carcinomas (most commonly lung and renal) can all manifest as soft tissue masses. A history of radiation therapy is a known risk factor for developing a soft tissue sarcoma. The patient should be screened for a personal or family history of genetic conditions associated with increased risk of developing soft tissue sarcomas. Li-Fraumeni syndrome is a germline mutation in tumor protein 53 that predisposes a patient to developing multiple cancers at a young age. Increased rates of soft tissue sarcomas are seen in patients with Gardner syndrome, also known as familial polyposis coli. Neurofibromatosis type I is a defect in the tumor suppressor gene NF1 on chromosome 17 that is inherited in an autosomal dominant fashion. Patients with neurofibromatosis can develop malignant peripheral nerve sheath tumors. An enlarging, increasingly painful neurofibroma should raise the suspicion of this development.
A thorough physical examination is a key part of the workup for a soft tissue mass. The patient should have the implicated extremity fully exposed, as well as the contralateral extremity to allow for the detection of subtle asymmetries. The size and depth of the mass should be noted. Larger than 5 cm is a risk factor for malignancy. Masses that are adherent to the fascia, or are located deep to the fascia, have an increased likelihood of being malignant. A mass that is mobile with the nearby musculature relaxed, and remains mobile when the musculature contracted is likely to be superficial in nature. A neurovascular examination should be performed and compared with the contralateral side. A positive Tinel sign at the mass is suggestive of a peripheral nerve sheath tumor.
The skin around the mass should be closely inspected. A mass with cutaneous ulceration is more likely to be a skin cancer, such as a squamous cell carcinoma, than a sarcoma. However, this finding can be seen in soft tissue sarcomas that have become large enough to be fungating. The presence of axillary or groin freckling, as well as café au lait spots, may be present in patients with neurofibromatosis. Tenderness, erythema, and fluctuance are characteristic of an abscess. A palpable or audible thrill indicates a vascular lesion, such as an aneurysm. In the setting of trauma or a coagulopathic state, a hematoma can manifest as a soft tissue mass. In these scenarios, the presence of ecchymosis should be assessed on examination. In the absence of ecchymosis, a diagnosis of hematoma should not be made without further work-up. Care should be taken to assess for lymphadenopathy. Prominent lymphadenopathy is a possible finding in lymphoma; some soft tissue sarcomas, however, do have the capacity to metastasize via the lymphatic system.
Radiographic findings
Although plain radiographs are a part of the work up for most soft tissue masses, findings are most often nonspecific. However, there are several findings that are characteristic of some soft tissue masses. Phleboliths are smooth, round, radiodense calcifications within venous structures that are suggestive of hemangiomas, the most common soft tissue tumor in children ( Fig. 3 ). Lipomas, the most common soft tissue tumor in adults, may demonstrate an area of increased radiolucency within a more radiodense area of skeletal muscle when they are intramuscular ( Fig. 4 ). Mature-appearing trabecular bone around the periphery of a soft tissue mass in the setting of recent trauma to the area is suggestive of myositis ossificans ( Fig. 5 ). In this clinical setting, a CT scan would be an appropriate next step to demonstrate peripheral ossification of the lesion. Occasionally, soft tissue sarcomas can demonstrate central, disorganized patterns of mineralization on radiograph ( Fig. 6 ). It is uncommon for soft tissue sarcomas to cause changes to adjacent bone. However, when they do, it may take the form of cortical thickening, periosteal reaction, or bony erosion.
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