DSRCT, or desmoplastic small round cell tumor, is a rare and aggressive type of soft tissue sarcoma that typically grows in the abdomen and pelvis. It primarily affects young males, with a median age at diagnosis of 25, and roughly 84% of cases occur in men. The name describes what the tumor looks like under a microscope: small, round cancer cells surrounded by dense, scar-like connective tissue (the “desmoplastic” part).
Where DSRCT Grows and Why
DSRCT most commonly develops in the peritoneum, the thin lining that covers the organs inside your abdomen. Tumors can appear as multiple masses scattered across the abdominal and pelvic lining rather than as a single growth in one organ. This pattern of spread along tissue surfaces, rather than originating within a specific organ, is part of what makes DSRCT unusual compared to more common cancers.
The cancer is driven by a specific genetic error: a piece of chromosome 11 breaks off and fuses with a piece of chromosome 22. This creates an abnormal gene called EWSR1-WT1, which produces a fusion protein that doesn’t exist in healthy cells. That protein acts as a powerful activator, switching on genes that drive uncontrolled cell growth. Importantly, this genetic change is not inherited. It happens spontaneously in a single cell during a person’s lifetime.
Common Symptoms
Because DSRCT grows in the abdomen, early symptoms are often vague and easy to attribute to other conditions. Most people notice abdominal pain, bloating, or a feeling of fullness. A growing mass may become large enough to feel through the skin. Some people experience changes in bowel habits, nausea, or unexplained weight loss. By the time symptoms become noticeable enough to prompt medical attention, the disease has often spread to multiple sites within the abdomen, and sometimes to the liver or lungs.
How DSRCT Is Diagnosed
Diagnosing DSRCT requires a tissue biopsy, because imaging alone cannot distinguish it from other abdominal cancers. Under the microscope, pathologists look for the characteristic pattern of small, round blue cells surrounded by dense fibrous tissue. But appearance alone isn’t enough, since several other cancers (Ewing sarcoma, rhabdomyosarcoma, neuroblastoma) also feature small round cells.
Two key tests confirm the diagnosis. First, immunohistochemistry staining checks whether the tumor cells produce an unusual combination of proteins. DSRCT cells co-express markers from multiple tissue types, including keratins and EMA (typically found in epithelial tissue), desmin (a muscle protein), and WT1. This multi-lineage staining pattern is distinctive. Second, molecular testing looks for the EWSR1-WT1 gene fusion itself, which is essentially the fingerprint of this cancer. Finding that fusion confirms the diagnosis.
Treatment Approach
DSRCT is treated with a combination of chemotherapy, surgery, and sometimes radiation, delivered in a carefully sequenced plan. Chemotherapy typically comes first, usually six cycles using drug combinations originally developed for Ewing sarcoma. These regimens alternate between different drug cocktails to attack the cancer from multiple angles. The goal of upfront chemotherapy is to shrink the tumors enough to make surgery feasible.
Surgery aims to remove all visible disease from the abdomen, a procedure called complete cytoreductive surgery. Because DSRCT tends to coat abdominal surfaces rather than form a single removable mass, this surgery can be extensive. Both chemotherapy and complete surgical removal have been associated with improved survival, making them the cornerstones of treatment. Whole abdominal radiation therapy is sometimes added after surgery, though its benefit is less clearly established.
When the cancer returns or stops responding to initial treatment, second-line chemotherapy options include different drug combinations. These regimens have shown activity against resistant disease, but responses tend to be shorter than with first-line treatment.
Prognosis and Long-Term Outlook
DSRCT carries a difficult prognosis. It is one of the more aggressive sarcomas, and the five-year survival rate remains low, generally estimated in the range of 15% to 25% depending on the extent of disease and how completely it can be surgically removed. Patients who achieve complete surgical removal after chemotherapy tend to do meaningfully better than those with residual disease. In one institutional series, patients whose scans showed no remaining disease after treatment had progression-free survivals ranging from 2 to 10 years.
Recurrence is common even after apparently successful treatment. In the same series, one patient developed lung metastases three years after diagnosis despite initial response. Follow-up typically involves regular imaging, often combining PET/CT scans with contrast-enhanced CT. PET/CT has proven particularly useful when standard imaging findings are unclear, helping distinguish scar tissue from active tumor.
Targeted Therapies Under Investigation
Because DSRCT is driven by a single fusion protein, researchers are working to develop treatments that attack the cancer’s specific molecular vulnerabilities. Several approaches are moving toward or into clinical trials. Some target proteins that the fusion gene forces the cancer to depend on, including growth factor receptors and cell-cycle regulators. Others use immunotherapy strategies aimed at surface markers that DSRCT cells display at unusually high levels, such as a protein called B7-H3. There is also interest in therapies that target fragments of the fusion protein itself, training the immune system to recognize and destroy cells carrying it. Combination strategies pairing these targeted approaches with existing chemotherapy are a particular focus.