Dr Daleen Geldenhuys describes where sarcoma cancer forms in the body, how it can be treated and the likelihood of progression.
Sarcomas are different to carcinomas. They arise from a different layer of tissue that can be best understood by knowing the embryological origin of tissues in the body.
The trilaminar or three-layered disc (embryo) develops three weeks after conception. It consists of the ectoderm, mesoderm and endoderm. These layers are arranged on top of each other. The mesoderm will become the cartilage, bone, fascia, smooth or skeletal muscle, blood vessels, lymph vessels and coverings of organs, such as mesothelium. Sarcomas are tumours that arise in these tissues. They are generally big and bad.
Bone and soft tissue sarcomas can be found in any part of the body.
Soft tissue sarcomas
Most soft tissue tumours of various tissue types are classified as either benign or malignant. Many are of an intermediate nature, which typically implies aggressive local behaviour with a low-to-moderate chance of distant spread.
When seen on imaging, such as MRI or CT scan, the tumour may appear to have a capsule. Soft tissue sarcomas have a propensity for local recurrence. Because recurrences are more difficult to treat than the primary lesion, complete resection and appropriate use of radiation are critical during the initial treatment.
The pseudo capsule provides surgeons with a more or less obvious plane of dissection. However, such an excision can leave behind microscopic or occasionally gross tumour. This may lead to local recurrences in as many as 80% of patients.
Post-operative radiation decreases the risk of recurrence associated with close margins. Often pre-operative chemotherapy will be necessary to shrink the tumour for better resection.
Regional lymph node involvement is rare in soft tissue sarcomas; fewer than 4% of cases have nodal metastases at presentation. Lymph node involvement is more frequent in certain subtypes, such as epithelioid sarcoma, rhabdomyosarcoma, synovial sarcoma, and clear cell sarcoma.
Some carcinomas and melanomas (skin cancer) should be included in the differential diagnosis for any mass presenting with lymph node metastases.
Many patients with high-grade soft tissue sarcomas, as well as a few with the low-grade type, progress to metastatic disease, even after adequate local control of the primary tumour has been achieved. The lung is the most common site of metastasis, which occurs in up to 50% of patients with high-grade lesions.
Although most patients don’t have clinically evident metastases at the time of presentation, they may have occult micro metastases that eventually manifest clinically.
Benign soft tissue tumours occur at least 10 times more frequently than malignant ones.
The incidence of soft tissue sarcomas ranges from 15 to 35 per 1 million population. The incidence increases steadily with age and is slightly higher in men than in women. Malignant soft tissue tumours occur twice as often as primary bone sarcomas.
Approximately 45% of sarcomas occur in the lower extremities, 15% in the upper extremities, 10% in the head and neck region, 15% in the retroperitoneum, and the remaining 15% in the abdominal and chest wall.
Certain types of soft tissue tumours occur in different age groups. Rhabdomyosarcoma is seen more frequently in children and young adults. Synovial sarcoma arises in young adults. Benign deep masses in adults usually are due to intramuscular lipoma.
In general, the prognosis in older patients with a diagnosis of high-grade sarcoma is poor.
As with tumours of other tissues, a direct relation exists between the size of soft tissue sarcomas and outcome. The larger tumours have a worse prognosis.
Superficially tumours (skin and subcutaneous tissue) have a relatively better prognosis than deep-seated lesions (inter/intramuscular, retroperitoneal) of similar histologic type. Probably because they are considerably smaller at the time of excision.
Multi-disciplinary and multi-modality approach
Soft tissue sarcomas are challenging lesions that demand a multi-disciplinary and multi-modality approach for proper clinical evaluation and treatment.
In the past, high-grade extremity sarcomas were treated with amputation but now limb-sparing therapies for these tumours are well-established today. Successful management of such lesions requires a multi-disciplinary team of surgeons, radiologists, pathologists, medical oncologists, radiation oncologists, oncology nurses, rehabilitation therapists, and social workers.
MEET THE EXPERT – Dr Daleen Geldenhuys
Dr Daleen Geldenhuys is a specialist physician and medical oncologist who works at West Rand Oncology Centre at Flora Clinic. She treats patients with all types of cancer and enjoys clinical research, and is a member of SASMO, SASTECS, ESMO and ENETS.
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