What is Spindle Cell Sarcoma?

Spindle cell sarcoma is an extremely rare bone cancer. It makes up only 2-5% of all types of bone cancer and typically presents in people over 40 years of age. Spindle cell sarcoma is a soft tissue tumor usually found in the arm or leg bones, or in the pelvis. 

Spindle cell sarcoma gets its name from the way it is shaped. Under a microscope, the cancer cells are long and narrow, giving it a spindle-shaped appearance. There are three types of spindle cell sarcoma of the bone. The types include, pleomorphic undifferentiated sarcoma, fibrosarcoma, and leiomyosarcoma.

Spindle cell sarcoma can develop in any bone of the body, but it is more commonly found in the longer bones, such as the femur (thigh bone), tibia (shin bone), area around the knee, or the humorous (upper arm bone). Furthermore, in undifferentiated sarcoma, the tumor develops in the pelvis, and with fibrosarcoma, the tumor develops in the head and neck area.

Types of Spindle Cell Sarcoma

There are three different types of spindle cell sarcoma. Although the tumors typically form in the longer bones of the body, in some of the types, the cancer cells can develop in the pelvis or head and neck region. The three types include:

• Pleomorphic undifferentiated sarcoma. Previously known as malignant fibrous histiocytomas (MFH), this type of sarcoma does not consist of any specific specialized cell. The cancer cells are undeveloped, making it difficult to determine what cell type they developed from. This type usually affects older populations, between 60-70 years of age.
• Fibrosarcoma. This type of sarcoma is extremely rare and is usually found in middle-aged adults. Fibrosarcoma consists mostly of specialized cells called fibroblasts. Fibrosarcoma typically develops in the femur (thigh bone).
• Leiomyosarcoma. This type of sarcoma is extremely rare and generally affects middle-aged adults. It is defined by the presence of specialized cells known as differentiated smooth muscle cells. It is managed similarly to osteosarcoma, which is a much more common bone cancer.

Symptoms

Spindle cell sarcoma can form in any bone of the body, which makes symptoms dependent on the individual and the location and type of spindle cell sarcoma. Often, symptoms of spindle cell sarcoma are common to other conditions, making it difficult to diagnose early on. Symptoms include:

• Bone pain that can come and go
• Pathological bone fracture due to weakening of the bone from the disease
• Swelling
• Tenderness or soreness
• Appearance of a lump or mass
• Reduced mobility in the affected area, or in a nearby joint
• Fatigue
• Malaise

Causes

Initially, the production of spindle cells is a helpful part of the body’s natural healing process when injured. However, once the healing process is finished, if spindle cells continue to divide uncontrollably, a mass or tumor develops.

There are various causes and risk factors for spindle cell sarcoma. Genetic irregularities can contribute to the development of this type of cancer, as well as other diseases or conditions that increase the likelihood of developing spindle cell sarcoma. Risk factors include:

• Paget’s disease of the bone. This disease of the bone causes the bones to become weak and misshapen and can increase the risk for spindle cell sarcoma.
• Undergoing previous radiotherapy. This is only a risk factor if the sarcoma has developed in a bone that was in the field of radiation. Typically, the sarcoma will take up to 9 years or more to develop after exposure to radiotherapy. 
• Fibrous dysplasia. This is a common bone disorder that replaces normal bone tissue with undeveloped connective tissue. On rare occasions, this may lead to the development of fibrosarcoma.
• Bone infarction. This happens when the bone has a lack of blood and oxygen, causing the bone tissue to die.
• Osteomyelitis. This happens when the bone or bone marrow becomes inflamed.

Diagnosis

Diagnosis for spindle cell sarcoma is made in a similar way to other bone cancers and disorders. Often, symptoms of spindle cell sarcoma are non-specific and can be hard to diagnose initially. The symptoms will vary depending on the location and type of tumor. The earlier you can diagnose spindle sarcoma, the better the treatment outcomes. Patients are typically referred to a bone cancer specialist for further testing if cancer is suspected. Several different diagnostic tools are used to diagnose spindle cell sarcoma and they include:

X-ray

X-rays are taken of the affected bone, and typically of the joints above and below it. The x-rays will reveal if there is any swelling around the bone or any abnormal bone growth. On occasion, a chest x-ray may be taken if it is suspected that the cancer has spread to the lungs.

Blood tests

Blood tests include:

• Blood chemistry (urea and electrolytes) is tested, indicating whether salt, urea, and creatine are at normal levels. This will confirm if the kidneys are functioning properly.
• A full blood count, which will assess all the different types of blood cells in the blood
• Measuring red blood cells, which carry oxygen through the blood
• Measuring white blood cells, which are essential to the immune system
• Measuring platelets, which allow for clotting and scabbing of the blood
• Measuring the hemoglobin levels
• Liver function tests
• Erythrocyte sedimentation rate (ESR) assesses for levels of inflammation
• C-Reactive protein levels increase with inflammation
• Alkaline phosphatase (ALP) is measured to determine the presence of osteosarcoma

MRI scan

MRI’s use magnetic resonance imaging to detect any abnormalities in the bone or soft tissue and are used specifically in the case of a pathological fracture. A pathological fracture occurs when the bone has been weakened by the disease. The risk of the spindle cell sarcoma spreading and getting into the blood is more likely when there has been a pathological fracture.

CT scan

A computerized tomography scan (CT scan) takes multiple angled or cross-sectioned x-rays of the body, and a computer uses the x-rays to build a 3-dimensional image of the body. The scan can be especially useful in finding secondary tumors that may have spread to the lungs.

PET scan

A PET scan (positron emission tomography) is used to detect whether the cancer has spread or metastasized. The PET scan examines the entire body rather than only scanning the affected area. These scans can also assess how treatment is working.

Biopsy

A bone biopsy is performed by a specialist in orthopedic surgery or sarcoma radiology, and it is conducted at a bone cancer surgical center. The sample from the biopsy is sent to a pathologist who will test the specimen to determine whether the cells are cancerous. 

There are two types of biopsies, a needle biopsy and open biopsy. Needle biopsies are conducted under local anesthesia and are used much more frequently than an open biopsy. An open biopsy is conducted under general anesthesia and is typically only used when a needle biopsy is inconclusive, and further investigation is needed. 

Treatment

Treatment for spindle cell sarcoma will depend on the location and stage of the cancer. Typically, treatment is done over a series of phases and includes chemotherapy, surgery, and radiation therapy.

Chemotherapy

The first round of chemotherapy is administered before any surgery to help shrink the primary tumor and kill any cancer cells that may have spread throughout the body. Generally, this treatment uses 3 different chemotherapy drugs over the course of 10 weeks. Surgery may proceed the first round of chemotherapy, and the chemotherapy treatments will continue over the next several weeks. Chemotherapy is administered through injection, tablets, or liquid medicine.

Surgery

Surgery can be performed after the first round of chemotherapy, and the focus is on the primary tumor. Depending on the size and location of the tumor, there are different courses of action surgery can pursue to remove the tumor. 

Sometimes due to the location of the tumor, surgery is not possible. Doctors work hard to perform limb preservation surgeries, but there are times where the best course of action is to amputate a limb. The goal is to safely remove the tumor, while allowing the body to still function normally at the same time.

Radiation therapy

Radiation therapy is used after surgery on some occasions to ensure the destruction of all cancer cells. Typically, radiation therapy is used if the patient has not responded well to surgery or if the tumor was unable to be fully removed. This type of therapy works to reduce the chances of cancer cells returning later. Radiation therapy may also be used for patients who are not healthy enough for surgery and require treatment to manage symptoms of the cancer.