Bone and soft tissue tumors are rare and can be classified into benign and malignant lesions (tissue damage or. -changes) can be subdivided into. Early and correct diagnosis and therapy are decisive for the success of treatment. Therefore, if a tumor of the musculoskeletal system is present, a specialized center should be consulted.
If a tumor cannot be clearly classified by imaging, a tissue sample is performed to confirm the diagnosis. In the case of benign tumors, an observational approach is possible in some cases. Malignant tumors must always be removed completely by surgery. The decision on which therapy to adopt is always made on an interdisciplinary basis by a panel of experts. The prognosis depends on the type and degree of differentiation of the tumor. After surgical removal of a malignant tumor, systematic follow-up over several years is required.
Frequency
Tumors of the musculoskeletal system are very rare diseases and can be subdivided into bone and soft tissue tumors. Depending on the biological behavior, a distinction is made between benign and malignant tumors.
Benign tumors usually show a slow and spreading growth pattern without the formation of metastases (tumor metastases). Malignant tumors, on the other hand, often show a rapid and locally aggressive growth pattern with a high tendency for metastasis. Semi-malignant tumors, which locally exhibit the growth behavior of a malignant tumor, but metastasize only in rare cases, occupy a special position in this context.
The incidence of benign soft tissue tumors is estimated to be about 300 per 100.000 inhabitants. In the case of benign bone tumors, which are usually diagnosed by chance, the frequency of occurrence is not known for many tumor types.
Malignant bone tumors, also known as bone sarcomas, occur more frequently between the ages of 20 and 30. and the 40. The most common tumors are those that have spread to the skeleton and only account for about 0.2 percent of all malignant tumors. More than 70 percent are localized in the arms and legs, most of them in the area of the femur (Fig.1).
Soft tissue sarcomas, on the other hand, preferentially occur after the age of 50. The first signs of bone metastases. Their frequency is given as approximately one percent of all malignant tumors. The lower extremities close to the trunk are most frequently affected, accounting for about 45 percent (Fig.2). The ratio of soft tissue to bone sarcomas is about 10:1.
Accurate classification of bone and soft tissue sarcomas is essential for the therapy to be adopted. For example, malignant tumors are evaluated in terms of their degree of differentiation (grading). This is the extent, in which the tumor tissue deviates from normal, healthy tissue. Information on regional and systemic spread (metastasis) is also relevant.
Fig. 1: Malignant bone tumor (osteosarcoma) at the lower section of the femur (source: Univ.-Prof. Dr. Rudiger von Eisenhart-Rothe)
Fig. 2: Malignant soft-tissue tumor (liposarcoma) on the inner side of the thigh (Source: Univ.-Prof. Dr. Rudiger von Eisenhart-Rothe)
Causes and origin
Little is known about the development of most benign and malignant tumors of the musculoskeletal system. Rarely can favoring bone damage, genetic factors or environmental influences be identified as the cause of origin. For example, bone sarcomas can develop on the basis of an initially benign tissue change or a systemic skeletal disease.
A small number of malignant bone tumors are preceded by irradiation of the corresponding area as the presumed cause of the tumor (so-called radiogenic sarcomas).
In the development of soft tissue sarcomas, there seems to be a connection to contact with carcinogenic substances such as arsenic or asbestos. Furthermore, local factors such as chronic accumulation of lymphatic fluid also seem to increase the risk of occurrence.
symptoms and course
The symptoms in the presence of a bone or soft tissue tumor vary widely. Benign bone tumors often remain painless and are only noticed as an incidental finding, for example in the course of clarification of a sports injury. In the case of malignant bone tumors, symptoms of the affected bone are often reported as being load-dependent. In rare cases, a bone fracture without external force (pathological fracture) of the affected bone can be the first symptom.
Patients with soft tissue tumors of the extremities usually present with a palpable tumor. Benign findings are also mostly painless and show slow growth, often over a period of years. Malignant soft tissue tumors, on the other hand, can enlarge rapidly and cause local pain, especially when a certain tumor size is reached and irritation of the surrounding muscles or adjacent nerves occurs.
Diagnosis
Since pain is usually the first symptom in the presence of a bone or soft tissue tumor, rapid and correct clarification is crucial. First of all, a detailed medical history must be taken and a physical examination performed. It is important to obtain information about the nature and duration of the symptoms. Since pain in bone and soft tissue is often attributed by the patient to a previous injury (trauma), there is often a delay in the diagnosis. For this reason, general symptoms such as fever, unwanted weight loss or night sweats are also examined as part of the anamnesis (so-called B-symptomatics), as these are sometimes the first signs of the presence of a malignant tumor.
In the case of a suspected diagnosis of a bone or soft tissue tumor, radiological clarification is of decisive importance. After evaluation of the symptoms, an X-ray is first performed if a bone tumor is suspected. Accurate analysis of the bone pattern can provide a good estimate of the rate of growth and sometimes can already distinguish a benign from a malignant lesion.
Additional imaging by magnetic resonance imaging (MRI) is often required for further specific clarification. In this way, the extension within the bone as well as a possible involvement of surrounding structures can be made visible. The administration of a contrast agent is mandatory when performing an MRI for tumor diagnosis. In the case of unclear soft tissue proliferation in the extremities, magnetic resonance imaging is the examination of choice and should be performed primarily. Here, too, MRI can often establish a diagnosis or differentiate between benign and malignant tumors.
Due to the rarity and complexity of musculoskeletal tumors, diagnosis and therapy should be performed at a specialized center.
If the diagnosis cannot be made without doubt on the basis of imaging, the removal of a tissue sample (biopsy) is mandatory. In case of doubt, deeper soft tissue tumors (e.g., in the muscles) should also be biopsied, since tumors in this location are often low malignant sarcomas. This allows an exact tumor classification and ultimately a specific diagnosis. Furthermore, the degree of differentiation of the tumor can be determined and the potential for metastasis can be assessed.
If the biopsy has proven the malignancy of the tumor, a systemic examination in the form of a computed tomography (CT) of the lung and abdominal cavity is necessary to obtain information about a systemic tumor metastasis.
Since strict tumor surgical aspects must be observed when performing a biopsy, these should only be performed by experienced tumor orthopedists at a center.
Therapy and follow-up care
The decision on the therapy to be adopted should always be made by an interdisciplinary committee of experts (tumor board). This committee develops a customized treatment concept for each patient. The underlying type of tumor is decisive for therapy planning.
Tumors of the bone that can be clearly assigned to a benign form, do not endanger the mechanical strength of the bone and are painless, can generally be observed during the course of treatment. Benign soft tissue tumors that are cosmetically disturbing, painful or cause tumor anxiety should be surgically removed. This also applies to soft tissue damage with progressive growth and deep location in the tissue. However, the decision to do this must be made individually for each patient.
In the case of malignant bone and soft tissue tumors, surgical removal (resection) is the mainstay of therapy. In this case, complete resection of the tumor with maintenance of a safe distance from the surrounding tissue is crucial for prognosis and recurrence rates. When bone tumors are removed, the implantation of a special prosthesis (tumor endoprosthesis) is often necessary to bridge the resulting defect (Fig.3). In some cases, reconstruction of the defect with autologous bone, such as the fibula, is possible.
However, the treatment of malignant tumors is always carried out in close cooperation with other specialist disciplines such as radiotherapists or oncologists, as some types of tumors require additional radiotherapy or chemotherapy.
Fig. 3: Tumor endoprosthesis at the lower end of the thigh (distal femur replacement) (Source: Univ.-Prof. Dr. Rudiger von Eisenhart-Rothe)
Prognosis
The prognosis of malignant bone and soft tissue tumors depends mainly on the degree of differentiation of the tumor. Thus, the 5-year survival rate decreases for so-called "high-grade" tumors-tumors to 25 percent. These are tumors with low differentiation, which are already far advanced in their growth and whose tissue is already very different from the initial tissue.
Aftercare
While for benign tumors the time periods for local follow-up can be chosen individually, for malignant bone and soft tissue sarcomas a systematic follow-up is necessary to control the success of the therapy over years.
Advice for patients
This dictionary entry contains general information only and must not be used for self-diagnosis or self-treatment. It cannot replace a visit to the doctor.
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Author
Klinikum rechts der Isar of the Technical University of Munich – Clinic and Polyclinic for Orthopedics and Sports Orthopedics
Ismaninger street 22
81675 Munich