Soft tissue sarcomas are malignant tumours that arise from mesenchymal tissue.

Mesenchymal tissue includes bone and muscle tissue, fat and peripheral nerve tissue, as well as the tissue of blood and lymph vessels.

Sarcomas are divided into >50 subgroups according to their tissue origin (UICC 1997)

Most important tumour types:

- Liposarcoma approx. 19% (fatty tissue)

- Fibrosarcoma approx. 18% (connective tissue)

- Malignant fibrous histiocytoma 11% (connective tissue) = undifferentiated pleomorphic sarcoma (UPS)

- Leiomyosarcoma 7% (smooth muscle tissue)

- Rhabdomysarcoma (striated muscle tissue)

- Alveolar soft tissue sarcoma (striated muscle tissue)

- Angiosarcoma (vascular system)

- Haemangiopericytoma (vascular system)

- Synovial sarcoma (synovial tissue)

- Malignant peripheral nerve sheath tumour (MPNST) = malignant schwannoma (peripheral nerve tissue) - malignant melanocytic schwannoma (peripheral nerve tissue)

- Chondrosarcoma (cartilage tissue)

- Malignant mesenchymoma (mixed tissue)

- Epithelioid cell sarcoma

- Osteosarcoma of the soft tissue

- Sarcoma without further details ( Sarcoma NOS)

Soft tissue sarcomas occur in only approx. 1% of all malignant tumours in adults. In children, soft tissue sarcomas account for a much higher proportion of malignant tumours (approx. 10%). In Germany, around 850 adult men and 750 adult women are newly diagnosed with soft tissue sarcoma every year. Soft tissue sarcoma can develop at any age, but occurs more frequently between the ages of 45 and 55 or under the age of 15. Men are affected slightly more frequently than women.

Up to 40% of soft tissue sarcomas are localised to the lower extremities (legs). This is followed by the trunk, abdomen, arms and head and neck area. In around 10% of patients, metastases (tumour metastases) are already present at the time of diagnosis, especially lung metastases.

With the exception of a few specific types of sarcoma, the causes of soft tissue sarcoma are largely unknown.

In Kaposi's sarcoma, a herpes virus-7 (HHV-7) is probably involved in the development of soft tissue sarcoma. Under certain circumstances, soft tissue sarcoma can also develop after radiotherapy. Asbestos fibres, arsenic and vinyl chloride also increase the risk of developing soft tissue sarcoma. In individual cases, a genetic disposition can be recognised in hereditary 'Recklinghausen's disease'

In most cases, the affected person first notices a painless swelling, especially if the tumour develops on the extremities. If the soft tissue sarcoma is located in the abdominal cavity, it is often recognised very late, as it has been able to expand here unnoticed for a long time without causing any noticeable swelling. The location of the tumour is therefore decisive for the time of diagnosis and thus the start of treatment. Soft tissue sarcoma only causes pain when the pressure on the organs or nerves becomes too great. As with any malignant tumour, the same applies here: The earlier the tumour is detected, the greater the chance of recovery. Typical tumour symptoms such as weight loss and reduced performance do not tend to occur.

Routinely, a medical history, physical examination, ultrasound examination, computerised tomography (CT), magnetic resonance imaging (MRI) and biopsy (taking a tissue sample) are required to make a diagnosis. Additional examinations such as X-ray examination, FDG-PET or PET/CT or skeletal scintigraphy or angiography to visualise tumour vessels may also be necessary.

In order to be able to determine the most suitable therapy, it is necessary to determine exactly which subtype (histology) the soft tissue sarcoma corresponds to, what degree of differentiation (grading) it has and how far it has already spread before starting therapy. In other words, the tumour stage is determined. Grading and the TNM classification are used for this purpose (see tables below).

In the meantime, many complex examinations including immunohistology, FISH (fluorescence insitu hybridisation) and molecular pathological diagnostics are carried out on the tumour sample, so that the histology result is sometimes only available after 1-2 weeks.

Grading

Microscopic examination of the tumour tissue provides an indication of the malignancy of the tumour. This involves comparing the similarity of the cancer cells with the organ cells.

TNM classification

Tumour spread is determined by the TNM classification.

T stands for the size and extent of the primary tumour, N stands for the number of affected regional lymph nodes and M stands for the occurrence and localisation of distant metastases (tumour metastases).

Note:
A superficial tumour is located completely above the superficial fascia and does not infiltrate it.
A deep tumour is either located exclusively below the superficial fascia or above the fascia with infiltration of or through the fascia.
Retroperitoneal, mediastinal and soft tissue sarcomas of the pelvis are classified as deep tumours

Stage grouping for soft tissue sarcomas (UICC/AJCC 2010)

Metastases

The tumour can spread to the entire body via the blood or lymph vessels (=distant metastases).

The metastases have the same type of sarcoma as the primary tumour.
In such a case, lung metastases are therefore sarcoma metastases and not lung cancer.

The treatment methods depend on the stage of the tumour. The earlier a soft tissue sarcoma is detected, the more favourable the prognosis for the patient.

As soft tissue sarcomas are very rare in adults and occur in all regions of the body, treatment is not as standardised as for other types of tumour. Optimal therapy requires close cooperation between different specialist areas right from the time of diagnosis and is therefore only possible in centres with the relevant experience. Once a soft tissue sarcoma has been diagnosed by histology (after a sample has been taken from the tumour), a treatment plan is drawn up in a tumour conference (= SARK tumour board of the CCCU) with the participation of pathologists, radiologists, radiologists, surgeons and oncologists in order to coordinate the timing of possible treatments such as surgery, radiotherapy or systemic specific tumour therapy (cytostatic therapy = chemotherapy). The aim of the treatment is locoregional tumour control and the prevention of distant metastases with a curative strategy.
The latest findings in sarcoma treatment are taken into account, and patients can also take part in studies with new/promising substances.

Operations

Removal of the soft tissue sarcoma is the primary treatment method. Patients with a T1 tumour can often be cured by removing the sarcoma alone.

The success of an operation depends largely on the size and position of the tumour in relation to its neighbouring structures.

Soft tissue sarcomas often form tumour cell nests in the immediate vicinity of the original tumour, which cannot be seen on CT or MRI. For this reason, either a compartmental resection (removal of physical parts of the tumour) or a simple resection with a sufficient safety margin is performed. In the case of larger tumours, a compartmental resection must often be performed, i.e. the entire tissue of the affected tumour area (e.g. tumour in the thigh - thigh muscle group) must be removed. The aim is a wide resection with a sufficient safety margin to the healthy tissue (>= 1 cm on all sides).

Radiotherapy (neoadjuvant - adjuvant)

Neoadjuvant radiotherapy (before surgery)

If the soft tissue tumour cannot be removed in an unfavourable position or the tumour is too large (tumour is inoperable), an attempt is made to reduce the size of the tumour by radiotherapy until it can still be removed with a sufficient safety margin.

Adjuvant radiotherapy (after surgery)

In the case of poorly differentiated and undifferentiated (G3/G4) primary tumours that are larger than 5 cm, radiotherapy is usually sought after surgery.

If the soft tissue sarcoma could not be removed with a sufficient safety margin and a post-resection is not technically possible, adjuvant radiotherapy is often carried out to destroy any remaining cell nests.

Chemotherapy (systemic therapy with cytostatics) (curative - palliative)

The curative effectiveness of chemotherapy after surgery has not yet been sufficiently clarified. Chemotherapy must be discussed on an individual basis with a curative intention. In some cases, certain types of soft tissue sarcoma react positively to chemotherapy before or after surgery.

If the tumour disease is at an advanced stage and metastases are already present at various sites, systemic chemotherapy can be administered. The aim of chemotherapy is to reduce the tumour mass or at least prevent it from growing and can possibly alleviate tumour-related symptoms.

Palliative (symptom-relieving) chemotherapy is used as standard to alleviate symptoms and may prolong life.

Regional therapies such as hyperthermia in combination with chemotherapy or isolated limb perfusion (ILP) can be offered in special centres (Munich, Heidelberg/Mannheim) for very large limb tumours. If necessary, patients are referred to these centres.

Amputation

If it is ultimately not possible to surgically remove the soft tissue sarcoma while preserving a sufficiently functional limb, amputation of the affected limb cannot be avoided in some cases. Reconstructive surgery and plastic surgery have the technically demanding task of compensating for tissue loss and restoring mobility as far as possible.

In principle, surgery is also the treatment of choice here. Complete removal of recurrence and/or a few metastases after complete successful removal of the primary tumour offers the best chance of remaining tumour-free for a long time.

In most cases, systemic therapy will be necessary (chemotherapy or targeted therapy, possibly participation in a clinical trial)

All patients with treated soft tissue sarcomas are offered follow-up care in the special outpatient clinics of the University Hospital with scheduled checks of medical history, physical examination, laboratory tests and the use of imaging procedures. The examination intervals are individualised, usually at 2-3 month intervals. Follow-up treatment is initiated by qualified social service staff during the inpatient stay.

The prospect of a cure depends crucially on the grading and size of the primary tumour as well as the spread of the tumour to other organs. Patients who are younger than 60 years old and have a well-differentiated tumour measuring less than 5 cm have a good chance of recovery.

In the case of well-differentiated tumours and without existing metastases, approx. 76% of patients have not shown a relapse of the disease after 5 years following successful treatment and can therefore be considered cured.

The more poorly differentiated the primary tumour, the higher the relapse rate. In the case of moderately differentiated soft tissue sarcomas, 56% of patients survive for at least 5 years. For poorly differentiated tumours, the figure is 26%.