Introduction

A sarcoma is defined as an extremely rare type of cancerous tumour that can affect your soft tissues, connective tissues, and bones. Spindle cell sarcoma (SCS) is one of many types of sarcoma, and its name is based on how this type of tumour looks under the microscope:a long, thin rod shape.

When individuals speak about soft tissue sarcoma, they typically refer to  tumours that may develop in the:

• Muscles
• Ligaments and tendons
• Lymph vessels
• Blood
• Fat
• Nerves
• Fibrous tissue (e.g., the cartilage in your joints)

Connective tissue is found in all parts of the body and can be thought of as a wrapper and container for your organs, muscles, and bones.¹

SCS can be further separated into 3 categories that will be described below:

1. Leiomyosarcoma
2. Fibrosarcoma
3. Undifferentiated pleomorphic sarcoma

Leiomyosarcoma

This type of SCS typically develops in the smooth muscle and the cells that eventually turn into smooth muscle cells, known as mesenchymal cells.² Smooth muscles are the types of muscle we do not have voluntary control over, e.g., the stomach and our intestines.

Out of all the different types of sarcoma, Leiomyosarcoma is one of the most common, accounting for 10-20% of all sarcomas.³ However, this is still reported to occur in less than one person in every 100,000 people every year.³ It is usually found in the large blood vessels, abdomen, and in women particularly in the uterus. However, when leiomyosarcoma does develop in the limbs, it most often forms in the upper leg (thigh).

Fibrosarcoma

Fibrosarcoma develops from cells called fibroblasts, which are cells that make up our connective tissue, such as tendons and ligaments, and the tissue that wraps around organs, known as fascia. Fibrosarcomas typically develop in the tendons (the structures which connect muscle to bone) but can develop in bones as well. Therefore, fibrosarcoma tends to develop more in the arms, legs, head, and neck.⁴

Because fibrosarcomas usually develop in the deep soft tissue and the fascia, successfully diagnosing this type of spindle cell sarcoma can be delayed. Unfortunately, fibrosarcoma is more likely to be diagnosed when more serious symptoms develop. Such symptoms include the restriction of blood flow to the area of the tumour or the nerves around the tumour being compressed.⁴  

Undifferentiated pleomorphic sarcoma

This category of SCS is also known as malignant fibrous histiocytoma (MFH) and predominantly develops in the soft tissues, including the retroperitoneum (connective tissue behind the stomach), but it can also develop in bones.⁵

Undifferentiated pleomorphic sarcoma (UPS) is believed to affect less than 1 in every 100,000 people in Europe, and a review of SCS patients reported that UPS is observed more frequently in white men in their 50s.⁵

UPS tends to appear as a fast-growing mass forming under the skin, and it most often affects the arms and legs more than other body parts, followed by the retroperitoneum.⁵

Who is most affected by spindle cell sarcoma?

Spindle cell sarcoma can develop in all ages; however, it mostly affects people aged 50 or older 6, and because of how rare this type of cancer is, most of the information about SCS comes from case studies of individual patients.

There are approximately 100 different subtypes of sarcoma, but overall, sarcoma is a rare type of cancer. But just how rare?

Sarcomas that form within the bone are reported to occur in less than 1 person in every 100,000 people per year.⁷  Additionally, all SCSs combined (excluding gastrointestinal stromal tumours) in Europe affect 4-5 people for every 100,000 people, making SCS an even rarer occurrence.³

According to Surveillance Epidemiology and End Results Program (SEER) data from 3299 SCS patients, the majority (79%) of SCS patients were white, and the average age of patients was 57 years.⁶  

Some of the risk factors for developing SCS include:

• Paget’s disease
• Osteomyelitis
• Fibrous dysplasia
• Previous radiotherapy treatment
• Bone infections causing death of bone cells.

What are the symptoms of spindle cell sarcoma?

Some symptoms of SCS can be rather nonspecific. For example, you may feel tired and under the weather, and you may also notice that you have lost weight without actively trying to or changing your diet.

Some symptoms may be more specific, but because spindle cell sarcoma is a very rare type of cancer, some of your symptoms may not be treated by doctors as sarcoma initially.

These specific symptoms could include:

• Bone pain
• Fractures in bone without trauma
• Swelling and lumps under the skin

How is spindle cell sarcoma diagnosed?

Several methods may be used to diagnose all categories of SCS, as it can be initially mistaken for other conditions because of how rare it is and how general the symptoms are in early stages.

The stage of SCS has been associated with the overall survival and disease-specific survival of patients, where SCS diagnosis at higher stages, e.g., stage 3 or 4, has been associated with poorer outcomes for patients.⁶ Therefore, it is important to be diagnosed correctly and as quickly as possible. The staging system is described below in this article.

Initially, a doctor will do a physical exam to look for any lumps and masses. The doctor will also ask you questions about the symptoms you have been experiencing and how long they have been going on.

Diagnostic scans

• X-ray - can identify changes in bone structure. It may also be used to identify if the cancer has spread to the lungs.
• Magnetic Resonance Imaging (MRI) - takes many different images of the soft tissues, as well as the head, neck, arms, and legs.
• Computerised Tomography (CT) - takes detailed images of bone and is a good tool for scanning the abdomen.
• Positron Emission Tomography (PET/CT) – a dye may be injected into your vein, which will help in highlighting areas of your body that are using lots of glucose because cancer uses up glucose faster than normal, healthy cells.

Blood tests

Although there is no specific blood test to diagnose SCS, certain blood tests may be requested by your doctor that can indicate if cancerous processes are happening in your body.

Examples of the routine blood tests your doctor will request include:

• White and red blood cell test
• C-reactive protein (CRP) test, which shows if there is inflammation in the body
• Lactate Dehydrogenase (LDH) test – LDH levels can be raised due to cancer.⁸

Specific cancer marker tests, which are blood tests that correlate to certain cancers, may also be requested. Tumour markers are molecules that are typically made by cancer cells and released into tissues and blood. They act as a beacon which can help doctors identify processes occurring within the body that are associated with specific types of cancers.

Biopsy

A definitive way to diagnose SCS is by removing a small piece of the tumour and looking at the specific cells that make up the tumour under the microscope. Doctors may then be able to tailor treatment to the specific type of tumour cells that are found. It is, however, a highly-invasive diagnostic approach.

How is spindle cell sarcoma staged?

The Tumour Node Metastasis (TNM) staging system developed by the American Joint Committee on Cancer (AJCC) is the system most often used to stage SCS.⁵

According to Cancer Research UK, TNM staging incorporates the size of the tumour(s), the number of nodes (lymph nodes) the cancer has spread to, and the level of metastasis (whether the cancer has spread to different areas of the body or not). The staging of SCS depends on where in the body the cancer has first developed (e.g., arms, legs, stomach, etc.).

Numbers are then given to stage cancer based on TNM; the stages range from 1-4, with stage 1 describing the smallest tumours that show little to no spread to lymph nodes, whereas stage 4 indicates that the tumour has grown and spread to lymph nodes and other areas of the body.

Several scans, including MRIs, CTs, and PET-CTs, are often used to stage SCS, as they can identify where SCS may have spread in different types of body tissues. For SCS in bone, a special scan known as bone scintigraphy may be used to look at physical and chemical changes in the bones.⁷ 

How is spindle cell sarcoma treated?

As SCS is an extremely rare form of sarcoma, treatment generally follows the same pathway as the treatments used for other types of sarcoma. The European Society for Medical Oncology (ESMO) recommends the following treatments for sarcomas that develop in bone, depending on the severity of the sarcoma: ⁷

The ESMO guidelines recommend the following treatment protocols for soft tissue sarcomas: ³

If possible, doctors will aim to remove a tumour with surgery, as research has shown that surgery is the treatment approach with the greatest chance of treatment success.⁶  However, the ability to perform surgery depends on where the cancer first developed (arms/legs or in the stomach area, etc.) and if the cancer has spread from where it first developed.

Chemotherapy and radiotherapy may be used before surgery to shrink tumours and improve the chances of surgery being successful. Chemotherapy and radiotherapy may also be used after surgery to ensure that all of the cancer has been removed. However, if patients cannot have surgery, radiotherapy and tailored chemotherapy regimens will be used as the first-line treatment.^{3, 7}

Targeted therapies

Targeted therapies aim to treat the specific types of cells found in tumours. Other specific treatments include immunotherapies, which encourage your immune system to fight cancer cells.^3,7

A lot of these targeted therapies and immunotherapies are currently being tested in clinical trials. More information on clinical trials for SCS and other soft tissue cancers can be found at Sarcoma UK.

Summary

SCS is an extremely rare type of cancer that can develop in various soft tissues, connective tissues, and bone. It is often differentially diagnosed as a soft tissue sarcoma, and early diagnosis is integral for better patient outcomes as SCS is known to spread quickly.

If possible, surgery is the first form of treatment and is associated with better prognosis for patients. Chemotherapy, radiotherapy, and targeted therapies may also be offered, especially if SCS has spread to other organs or distant areas of the body.