Desmoplastic small-round-cell tumor

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at July 29, 2016
StartDiseasesDesmoplastic small-round-cell tumor

The connective tissues of the body are tissues that are designed to support and connect organs, muscles, and skin within the body. If any of the cells in these connective tissues become cancerous, a person may develop a soft-tissue sarcoma. A desmoplastic small-round-cell tumor is a very rare type of soft-tissue sarcoma, and it grows extremely quickly.

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Definition & Facts

Desmoplastic small-round-cell tumors are cancerous tumors that tend to be large masses. They are characterized by desmoplastic stroma, which are an overgrowth of connective tissue, and dense, solid nests of small round cells.

This type of tumor is most often considered to be a childhood cancer because it frequently affects children and young adults. Though it is most common among males, females may also develop desmoplastic small-round-cell tumors. Desmoplastic small-round-cell tumors are extremely rare, and only about 20 new cases of this cancer are diagnosed each year.

Symptoms & Complaints

At first, the tumors associated with desmoplastic small-round-cell tumor do not really affect the body much, so there are not many warning signs in the early stages of this type of cancer.

The only early symptom is tumors that feel like a hard, dense, round mass, but when these tumors are growing deep within the abdomen, they may not be very apparent. Symptoms typically only become noticeable when the tumors are large enough to be putting pressure on organs and glands in the abdominal cavity.

Patients may experience a loss of appetite, and they often begin to lose weight. Patients might feel cramps in their abdomen, and they often suffer from abnormal bowel movements or constipation.

The tumors can cause feelings of fatigue and back pain. Fluid often begins to collect in the abdominal cavity, and the tumorous masses can grow to very large sizes. Therefore, the cancer progression often causes abdominal swelling and abdominal distension.

If the tumors are growing near the thyroid or other glands that produce hormones, a person with a desmoplastic small-round-cell tumor might have thyroid conditions or hormonal imbalances. Other possible symptoms include kidney issues, difficulty urinating, anemia, and blood clots.

Causes

Like all other types of cancer, desmoplastic small-round-cell tumors are caused by cells that become damaged and start to divide and spread without control. Desmoplastic small-round-cell tumors are always accompanied by a unique error in two chromosomes that control cell growth. The EWS gene on chromosome 22 becomes fused to the WT1 (Wilms tumor protein) gene on chromosome 11, and the resulting protein cannot control or suppress cell growth properly.

People with this condition are more likely to be young and male. The reason that desmoplastic small-round-cell tumor most affects children is that it is formed by primitive cells. Primitive cells are immature cells used to grow other types of cells within the body. Children have higher amounts of primitive cells than adults, so they have more cells that can turn into a desmoplastic small-round-cell tumor.

General risk factors for cancer apply to these types of tumors. This means that exposure to carcinogenic chemicals and environmental pollutants may increase a person's chance of developing a desmoplastic small-round-cell tumor. 

Diagnosis & Tests

Diagnosis for desmoplastic small-round-cell tumor typically begins with the discovery of bulky, dense masses in the abdominal cavity or pelvis. Often, the tumors are 10 centimeters or larger before they are discernible during a physical examination. Sometimes they are discovered earlier if the patient is undergoing an abdominal surgery or imaging tests for unrelated reasons.

Once the tumor is discovered, a biopsy will be needed to determine whether the tumor is malignant. A biopsy will show whether the cells are aggressive and cancerous. There are many types of round cell tumors, so sometimes desmoplastic small-round-cell tumor can be confused for another type of round cell tumor, such as Ewing's sarcoma.

However, an analysis of a tumor sample will help to diagnose it specifically because this type of analysis will reveal the signature protein caused by the EWS-WT1 fusion. Once the protein that characterizes this type of cancer has been discovered through analysis, the diagnosis will be confirmed. Since desmoplastic small-round-cell tumors are often associated with multiple, aggressive tumors, an imaging test will typically be required to determine the extent of the cancer. 

Treatment & Therapy

Since desmoplastic small-round-cell tumors are so aggressive and spread so quickly, the five-year survival rate for patients is roughly 15 percent. However, the prognosis for patients with desmoplastic small-round-cell tumor is improving as treatment methods become more advanced. Basic options for treating this condition are surgeries to remove the tumors, radiation therapy, and chemotherapy.

The precise treatment plan will depend on the location and severity of the cancer. For example, if it is caught relatively quickly and still contained to the abdomen, a doctor may just recommend surgery to remove the tumors before the cancer can spread. Even if all cancerous cells cannot be removed with surgery, it is still often needed to remove large tumors that are putting pressure on other organs or harming bodily functions.

However, if the cancer has metastasized to lymph nodes, the liver, bones, or the lungs, extensive chemotherapy and radiation may be required. Chemotherapies that are often used to treat desmoplastic small-round-cell tumors include etoposide, doxorubicin, cyclophosphamide, vincristine, and ifosfamide.

Stem cell transplants can help to alleviate some of the effects of high-dosage chemotherapy. Some new therapies are molecularly targeted, so they make it easier to kill cancerous cells without destroying healthy ones. 

Prevention & Prophylaxis

So far, there are no specific methods that can be used to reduce a person's chances of getting a desmoplastic small-round-cell tumor. Instead, doctors focus on regular screenings that can catch this type of tumor at an earlier stage. Though this does not actually prevent the cancer, it at least ensures that a patient has a better chance of surviving the disease.