What is Soft Tissue Clear Cell Sarcoma?

Clear cell sarcoma of soft tissue (CCSST) is an extremely uncommon type of tumor that begins in cells called neural crest cells. These cells become clear due to a buildup of a substance known as glycogen inside them. This rare tumor has similar features to a skin cancer known as malignant melanoma when studied under a microscope. Most often, these tumors can be found in the protective covers of tendons and muscles, usually in the lower parts of the body like the ankles. Tumors appearing in the upper body parts are less common. There have been very few reports of this tumor originating in the chest wall and tissues around the shoulder blade.

What Causes Soft Tissue Clear Cell Sarcoma?

The exact cause of some types of tumors, including soft tissue sarcomas, isn’t fully understood. However, some factors have been linked to an increased risk. These include genetic factors, exposure to radiation therapy, a condition called lymphedema affecting the lymphatic system, changes in genes (mutations), and the use of chemotherapy.

Clear cell sarcoma, a type of soft tissue sarcoma, was initially seen as similar to malignant melanoma based on their similar microscope appearances (‘histological similarities’). Both of these conditions share common markers in lab tests, and studies of their genes suggest they are closely related.

One major difference between malignant melanoma and clear cell sarcoma is that most clear cell sarcomas are associated with a specific rearrangement of chromosomes, known in medical terminology as a t(12;22)(q13-14;q12) translocation.

Essentially, this simply means that pieces of two chromosomes have swapped places. This unusual rearrangement is not generally seen in malignant melanoma.

Risk Factors and Frequency for Soft Tissue Clear Cell Sarcoma

The exact number of cases of this type of cancer, known as clear cell sarcoma, is unknown. It seems to be more common in Caucasians, and appears to affect men and women equally. The average age of diagnosis is 39, though it can also occur in children but very rarely. Most commonly, this cancer develops in the lower parts of the body, especially around the foot and ankle, but it has been found in other areas like kidneys, trunk, penis, digestive system, and head and neck area. Survival rates for this cancer vary depending on the stage it’s diagnosed at, with 50% and 38% of patients surviving for 5 and 10 years respectively. However, those diagnosed at later stages (III and IV) often have lower survival rates.

Signs and Symptoms of Soft Tissue Clear Cell Sarcoma

People usually get CCSST, a condition that often appears as a small tender spot or swelling in the legs or thighs, when they are in their thirties or forties. In some cases, CCSST can affect the tissue beneath the skin and nearest to it, which might lead to skin ulcers. Though it’s uncommon, CCSST has been found in other places of the body like the lower back, neck, around the pharynx (a part of the throat), and even the penis.

Testing for Soft Tissue Clear Cell Sarcoma

When a doctor first examines you for signs of a potential issue, they will usually start by asking about your medical history and then performing a physical exam. If you’ve noticed a small swelling or tender spot in your lower leg, particularly around the ankle, your doctor will want to know when you first noticed it and if it’s been growing. Physical signs like the size of the lump, its depth, whether it’s attached to surrounding tissues, swelling, or signs of nerve or blood vessel involvement, will all be looked at closely.

Different types of soft tissue sarcomas exist, and to find the best image of each one, different imaging techniques may be used. Along with standard X-rays, which show possible masses growing from the bone or calcifications within the mass, magnetic resonance imaging (MRI) is typically the go-to option for masses located in the extremities. MRIs, as compared to CT scans, are superior in detailing different muscle groups and provide more information about the reach of these tumours. However, CT scans can be useful if the mass is large (over 5 cm) or located deep within the body, because it provides important information about whether the disease has spread.

For planning further tests and treatment, a small sample of the tissue, or a biopsy, will be taken. This collection of tissue can happen through an incision, a fine needle aspiration, or a core needle biopsy. The last method is usually the preferred option, as it is highly accurate and has a lower risk of complications. The tissue sample will be further examined for confirmation of a soft tissue sarcoma and to determine the type of the tumor. This involves a process called immunohistochemistry, where certain markers are looked for within the cells. Additionally, techniques like fluorescence in situ hybridization (FISH) or reverse transcription-polymerase chain reaction (RT-PCR) are used to distinguish the tumour from other similar-looking ones.

After you have been treated, your doctor will want to keep an eye on things to ensure the treatment has been successful. This usually involves getting another scan about three months after treatment. If the initial diagnosis was a high-grade lesion, doctors prefer to get these follow-up images every three to six months. For low-grade lesions, these check-up images can be on an annual basis.

Treatment Options for Soft Tissue Clear Cell Sarcoma

If you have a localized lesion, that is a growth or spot that’s limited to one specific area, the ideal treatment is to surgically remove it, while also ensuring no part of the lesion is left behind. This is known as a wide surgical resection with negative margins. When the surgery successfully removes the entire lesion, additional treatments are typically not required as such treatments may not necessarily increase the chance of survival.

However, if the lesion is not completely removed through surgery, there can be higher chances it may come back. In such cases, radiotherapy, which uses high-energy particles or waves like X-rays to destroy or damage cancer cells, might be considered as it could potentially improve the situation for patients.

Chemotherapy, which is a powerful drug treatment that kills rapidly growing cells in the body, is generally recommended for patients whose disease has spread to other parts of the body. Doctors may opt for a treatment regimen that includes cisplatin, in combination with doxorubicin, a type of chemotherapy that’s also known as an antitumor antibiotic.

After the surgery, it’s important for patients to have regular follow-ups as there’s a chance of the lesion coming back. Depending on how high the patient’s recurrence risk is, more frequent scans and tests might be scheduled, whereas, in lower-risk cases, scans might be scheduled on an annual basis.

When a tumor is found near the tendons and tie tissues in the body, doctors consider several possibilities to determine what it might be. The illnesses typically considered include:

‘Paraganglioma-like dermal melanocytic tumor,’ a skin tumor typically found in the hands or feet of female patients
‘Malignant Melanoma’ (MM), a form of skin cancer
‘Malignant peripheral nerve sheath tumor,’ a type of cancer that starts in the cells surrounding the peripheral nerves
‘Synovial sarcoma,’ a type of cancer that appears near joint spaces
‘Clear cell myomelanocytic tumor,’ which is part of a group of tumors that usually appear in the abdominal region

Each potential diagnosis has distinct characteristics. For instance, this particular tumor called ‘CCSST’ is usually found in younger patients, is situated in deep tissues, is associated with tendons, and usually does not affect the outer skin layer. There are also specific genetic markers that aren’t present in malignant melanoma but can be found in CCSST. However, these two types of tumors can have similar appearances under a microscope, which can make diagnosis more challenging.

‘Synovial sarcoma’ has its gene markers too, which doesn’t appear in CCSST. On the other hand, ‘paraganglioma-like dermal melanocytic tumors’ generally forms a lumpy growth in the skin of female patients and has identifiable traits when examined under a microscope.

More so, ‘Clear cell myomelanocytic tumor’ is part of a larger family of tumors and is usually found in the abdomen, especially in the ligaments of the liver. The ‘Malignant peripheral nerve sheath tumor’ typically develops within large peripheral nerves and tests negative for a specific protein called HMB-45.

What to expect with Soft Tissue Clear Cell Sarcoma

CCSST, or clear cell sarcoma of soft tissue, usually has an overall unfavorable outcome. This condition tends to worsen over time, and it’s often spread to other parts of the body when diagnosed. In a study involving 75 patients, it was found that 69% had the disease spread (metastasized), and local recurrence (the disease returning in the same place) was 21%. The overall survival rate for people with CCSST over 5 years was 47%, and over 10 years it was 36%. When looking at patients whose disease had not spread at the time of diagnosis, the survival rate was slightly higher: 55% at 5 years and 41% at 10 years.

Another study with 52 patients showed survival rates of 59% at 5 years, and 41% at 10 years. Important factors that affect the prognosis include the size of the tumor, how deeply it has invaded the body, and its TNM classification (a system to describe the extent of cancer’s spread). Of all these factors, only tumor size remained a significant predictor of outcome when researchers considered them all together.

Another point to note is that 10-14% of patients ended up with the cancer spread to their regional lymph nodes (small glands that produce and store cells that fight infection). A large number of patients with CCSST developed distant spread of disease, typically to the lungs and bones, as well as to regional lymph nodes. Overall, the progression of CCSST tends to be steady and aggressive, often resulting in the cancer spreading extensively throughout the body.

Possible Complications When Diagnosed with Soft Tissue Clear Cell Sarcoma

Many patients notice a slowly growing lump in their lower limb, but between 30% to 60% of patients may experience pain or discomfort. A small number of patients may even have a skin ulcer forming over the lump. If untreated, Clear Cell Sarcoma of the Soft Tissue (CCSST) can ultimately turn into a dangerous disease that spreads throughout the body.

Key Findings:

Many patients have a slowly growing lump in the lower limb.
Between 30% to 60% of patients may experience pain or discomfort.
A small number of patients may experience skin ulceration over the lump.
Untreated, CCSST may become a dangerous disease that spreads throughout the body.

Preventing Soft Tissue Clear Cell Sarcoma

Clear cell sarcoma of soft tissue (CCSST) often affects individuals in their 30s or 40s. Unfortunately, this disease generally has a poor outlook. Some patients may seem to be free of the disease after initial treatments, but later they may experience a return of the cancer or it may spread to other areas of the body, which tends to progress quickly and can be fatal.

It’s very important that patients fully understand this generally poor outlook of CCSST, and are aware of factors that may increase their risk of the cancer returning or spreading to other parts of their body. Doctors will provide information about the stage of the tumor (which explains how advanced or widespread the cancer is) both before and after treatment.

Patients are strongly encouraged to keep regular appointments with their healthcare providers. Regular check-ups allow doctors to monitor the patient’s condition and promptly address any new or recurring issues.