A Brief Guide to Sarcoma, Lumps and Bumps

 In Tumour

Sarcoma is an umbrella name for over 50 types of tumours that develop in the bones or soft tissues. Malignant sarcoma is considered a rare type of cancer, accounting for approximately 2% of all cancer diagnosis in Singapore, more than half of whom are over 60 years old. Sarcoma can occur at young ages. In fact, it is the 4th most common childhood malignancy, accounting for 15% of the cases locally. 

Though less common, sarcoma is a disease burden for families because it is aggressive and can leave survivors with disabilities, especially in children. Lack of awareness also plays a role in late diagnosis, thus less effective treatment and compromised survival rate. For instance, early stage localised sarcoma has a 5-year survival rate of over 80%. However, if the disease is detected when it has metastasised, the 5-year survival rate drops to a dismal 20%. 

This general guide to sarcoma aims to provide essential knowledge about this ‘forgotten’ cancer, including its definition, causes and risk factors, types, symptoms, staging, and treatment.

What is Sarcoma?

Sarcoma is heterogeneous, which means it can develop in a diverse range of connective tissues in the body. Depending on the type of tissues affected, sarcoma is categorised into 2 main types: 

  • Soft tissue sarcoma: develops in the soft tissues such as muscle, fat, nerves, blood vessels, fibrous tissues. The majority of sarcomas belong to this type. Some of the common subtypes in Singapore include Kaposi sarcoma, cardiac angiosarcoma
  • Bone sarcoma: develops in the tissues that form the bone such as the bone tissue, cartilage or bone marrow. 

Sarcoma can be benign or malignant, and can be found in various parts of the body, most commonly the limbs. Here is the distribution of sarcomas based on their location:

  • Lower extremities – 40%
  • Upper extremities – 15%
  • Head and neck – 15%
  • Trunk, chest wall, and abdomen – 30%

There are several lumps and bumps that could be mistaken for sarcomas. Being able to differentiate between these benign masses and sarcomas is essential to avoid unnecessary tests and patient suffering.

Sarcoma vs. Carcinoma

To better understand sarcoma, it is useful to differentiate it with carcinoma – the cancer type we are more familiar with.

The biggest difference between sarcoma and carcinoma is the type of tissues they originate from. Sarcoma develops from the connective tissue while carcinoma develops from the epithelial tissue which lines the surfaces of the body (i.e., the skin) or the internal organs, such as the lungs or the liver. When they spread, they do so differently. Carcinoma travels through the lymph system and sarcoma makes its way through the blood system. Carcinoma is far more common than sarcoma. While both types can occur to any age, sarcoma is more common in younger patients and carcinoma is more common in older patients.

Carcinoma and sarcoma may develop from the same organ in the body but because of their different origin and behaviours, they will require different treatments. Often, a biopsy is necessary to tell the exact type. An example is carcinoma and sarcoma of the gastrointestinal tract. When the digestive tract is affected with carcinoma, we might have a case of esophageal cancer, stomach cancer or colorectal cancer. But when sarcoma develops in the GI tract, it is likely to be a case of Gastrointestinal Stromal Tumour (GIST). Both types may show similar symptoms such as pain in the abdomen, blood in the stool, or loss of weight.

Differences between sarcoma and carcinoma

Common types of sarcoma

Depending on the location of the tumours and whether it is benign (ie., non-cancerous) or malignant (i.e., cancerous), we might be dealing with:

  • Benign bone tumours
  • Malignant bone tumours
  • Benign soft tissue tumours
  • Malignant soft tissue tumours
  • Genitourinary sarcomas (sarcomas of the genital and urinary organs)

The following sections will decipher these types of sarcoma.

Benign bone tumours

Benign tumours of the bone are significantly more common than their malignant counterparts. Some of these tumours include:

  • Osteochondromas
  • Non-ossifying fibromas
  • Aneurysmal bone cysts
  • Simple bone cysts
  • Langerhans Cell Histiocytosis

Some benign bone tumours can be a part of familial syndromes, such as McCune-Albright syndrome, Mffucci’s disease, and Ollier’s disease. Despite their benign nature, these tumours can be quite destructive, especially when they grow in confined spaces. 

Malignant bone tumours

These tumours are relatively rare and include:

  • Osteosarcoma (osteogenic sarcoma) – most common type of bone cancer
  • Chondrosarcoma – sarcoma of the cartilage cells of the limbs or pelvis
  • Ewing’s sarcoma – commonly arises in children’s pelvis and spine areas
  • Multiple myeloma – sarcoma of the plasma cells in the bone marrow
  • Fibrosarcoma of the bone – sarcoma of the fibrous tissue, often found in the lower limbs

Around one-third of all bone tumours get diagnosed in patients under the age of 35 years old. The vast majority of these cases occur in children.

When these tumours spread beyond the bone tissue, we start dealing with metastatic bone sarcoma. However, the opposite could also occur. A tumour that originates in a distant tissue could travel to the bone and form secondary bone cancer. Common tumours that follow this pattern are thyroid, lung, breast, kidney, and prostate cancers.

Benign soft tissue tumours

Out of all the lumps and bumps discovered, only 5% are cancerous. The remaining are benign soft tissue tumours. Depending on the location and size of the tumours, surgical treatment may be necessary. Desmoid tumours, however, require the intervention of medical oncology, radiation therapy, and interventional radiology.

Here are some common benign soft tissue tumours:

  • Desmoid tumours
  • Lipomas (fatty tumours)
  • Large arteriovenous malformations
  • Pigmented villonodular synovitis
  • Schwannomas
  • Synovial chondromatosis

Malignant soft tissue tumours

Most soft tissue tumours occur in adults, with the exception of rhabdomyosarcoma, which is an exclusive tumour of children. The most common malignant soft tissue tumours are:

  • Liposarcoma – Sarcoma of the fatty tissues
  • Leiomyosarcoma – Affects the muscle tissues, commonly of the organs in the pelvis and abdomen areas
  • Undifferentiated pleomorphic sarcoma (UPS) – Often affects the limbs
  • Angiosarcoma – Affects the inner lining of the blood vessels
  • Kaposi’s sarcoma – Develops in the cells of the skin or mucous membranes
  • Gastrointestinal stromal tumours (GIST) – Develops from the digestive organs.
  • Desmoplastic small round cell tumours (DSRCT) – Most commonly found in the abdomen and pelvis area
  • Malignant peripheral nerve sheath tumours (MPNST) – Affects the peripheral nerves
  • Rhabdomyosarcoma (RMS) – Usually affects the skeletal muscle tissues
  • Synovial sarcoma (malignant synovioma) – Affects the limbs, foot, near large joints (wrist or ankle). It can also form in soft tissues in the lung or abdomen.

Genitourinary sarcomas

Genitourinary sarcomas are malignant tumours that develop in the urinary tract or genitals. You can have genitourinary sarcomas in any of these organs:

  • The bladder
  • The kidney
  • Testicles
  • The ureters
  • The urethra
  • Prostate
  • The penis
  • The vagina

Causes and risk factors of sarcoma

Sarcomas tend to occur sporadically. In other words, individuals with no family history of cancer or exposure to cancer-precipitating factors can develop these tumours.

Risk factors that doctors have agreed on are limited and not specific, which poses a challenge to screening and prevention. With that said, some risk factors have been identified and include:

High doses of radiation – Recurrent sessions of radiation therapy can increase the risk of sarcomas. While this treatment modality is indispensable to treat some cancers, it remains a risk factor for sarcomas and other tumours.

Genetic conditions – Certain familial diseases can increase the risk of sarcomas. We covered some of these syndromes in the section above.

Exposure to chemicals – Chronic exposure to certain chemicals may increase the risk of sarcoma. Examples include vinyl chloride, dioxins, and phenoxyacetic herbicides.

Human herpesvirus 8 – Infection with human herpesvirus 8 increases the risk of Kaposi’s sarcoma. This is the only soft tissue sarcoma that has a well-defined cause.

Diagnosis of sarcoma

When you notice a lump that is large enough to raise concern, you should consult with your doctor. The general guide is to have all lumps of 4 centimetres or bigger diagnosed by a professional. This is especially important when the lump is getting bigger or causing you pain. Note that pain might not be obvious until the lump is big enough and presses on the nerves, blood vessels, muscles or other organs. 

With bone sarcoma, patients may feel a dull aching bone or joint pain in the area where the tumour arises. The tumour may also cause swelling or lump. In children, the pain can sometimes be mistaken for ‘growing pain’ or pain caused by minor daily injuries if the kids are active and involved in sports. However, it is always better to have the lump and pain checked by a professional than leave it to chance. 

At the doctor, the following diagnostic steps may be taken: 

  • Discussion about other symptoms you might be having (e.g., weight loss, night sweats, fever)
  • Discussion about your personal and family medical history
  • A complete medical examination
  • Biological tests
  • Imaging tests, such as X-rays, CT scans, an MRI, and in some cases, a PET scan
  • Laboratory tests

If you have been previously diagnosed with a type of sarcoma, the presence of a new growth may be an indication that the tumours are back (a relapse). However, before panicking, make sure to consult with your oncologist first.

Staging of sarcoma

Depending on the type of sarcoma you have (i.e., soft tissue, bone), staging might be different.

Soft tissue sarcoma stages include:

  • Stage 1 – Stage 1 is divided into stages 
    • 1A (smaller than 5 centimetres)
    • 1B (larger than 5 centimetres)
  • Stage 2 – Stage 2 is dedicated to certain tumours and includes:
    • 2A (smaller than 5 centimetres) 
    • 2B (larger than 5 centimetres) 
  • Stage 3 – Stage 3 is divided into 3A or 3B depending on the size of the tumours and whether or not it has reached nearby tissues.
  • Stage 4 – This stage translates to the spread of the tumours to distant parts of the body (e.g., lungs).

Bone sarcoma stages include:

  • Stage 1 – Stage 1 is divided into:
    • 1A (smaller than 8 centimetres) 
    • 1B (larger than 8 centimetres)
  • Stage 2 – Stage 2 is dedicated to certain tumours and includes:
    • 2A (smaller than 8 centimetres) 
    • 2B (larger than 8 centimetres) 
  • Stage 3 – Stage 3 is divided into 3A or 3B depending on the size of the tumours and whether or not it has reached nearby tissues.
  • Stage 4 – This stage translates to the spread of the tumours to distant parts of the body (e.g., lungs).

Treatment of sarcoma

After consulting with your GP or primary care physician and if sarcoma is suspected, he/she will refer you to a cancer specialist, ie., an oncologist. The specialist will conduct a comprehensive diagnostic testing to assess the size, limits, and involvement of the tumours.

Next, your doctor will propose one or more of the following therapeutic options:

Surgery – Doctors consider surgery to be the most effective treatment for sarcomas. For this reason, it is the most common therapeutic approach. The purpose of surgery is to remove the tumours with a safety margin to prevent relapses. During the procedure, your surgeon might take a tissue sample and send it to the pathologist for a quick analysis. This will determine how the rest of the surgery will go on. For instance, cardiac angiosarcoma can be challenging to resect due to the risk of bleeding.

In some cases when sarcoma has grown into the nerves and blood vessels, surgery to remove the entire limb, or an amputation, provides the best chance to eliminate cancer and survive. 

Radiation therapy – Ironically, radiation therapy is both a risk factor and a treatment modality for sarcomas. You can work with your physician to make an informed decision about whether the benefits of radiation therapy outweigh its side effects.

Chemotherapy – Researchers found that chemotherapy is more effective in treating bone sarcomas than soft tissue sarcomas. It might be employed before surgery to shrink the tumour and facilitate limb sparing surgery. Discuss with your doctor about the pros and cons of chemotherapy for your specific case. 

Biological therapies – Sarcomas that do not respond well to traditional treatments may benefit from biological therapies. Examples include Olaratumab (i.e., Lartruvo), which works best for soft tissue sarcomas that did not improve with previous treatments. Additionally, patients who received chemotherapy may benefit from the additional boost given by Pazopanib (i.e., Votrient).

Choosing between these treatments depends on the size of the tumours, the staging, expansion to other tissues, and of course, the consent of the patient.

Takeaway Message

Sarcomas are relatively uncommon tumours that are challenging to deal with at advanced stages. Identifying these tumours early on is a key way to limit their destruction and increase the chance of survival. Make sure you have all growing lumps checked by the doctor, especially if they cause pain. In most cases, they are benign. In the rare cases that they are not, catching sarcomas early provides the best chance for effective treatment, since screening for this cancer is not possible. 

Due to the limited data we have about the triggers of sarcomas, the only way to prevent them is by avoiding exposure to well-established risk factors. For cancer patients who need radiation therapy as part of the treatment for another type of cancer, be sure to discuss the risk of sarcoma with your oncologist and devise an optimal treatment for your case. 

We hope that this guide helps you appreciate the different aspects of sarcoma and how we can address it as regular people. Check with your doctor if you need tailored medical guidance about your individual risk of sarcomas.

 

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