Desmoplastic small round cell tumor

Desmoplastic small round cell tumor is classified as a soft tissue sarcoma. It is an aggressive and rare tumor that primarily occurs as multiple masses in the abdomen. Other areas affected may include the lymph nodes, the lining of the abdomen, diaphragm, spleen, liver, chest wall, skull, spinal cord, large intestine, small intestine, bladder, brain, lungs, testicles, ovaries, and the pelvis. Reported sites of metatastic spread include the liver, lungs, lymph nodes, brain, skull, and bones.

 The tumor is considered a childhood cancer that predominantly strikes boys and young adults. The disease rarely occurs in females, but when it does the tumors are often mistaken for Ovarian cancer.

Causes

There are no known risk factors that have been identified specific to the disease. The tumor appears to arise from the primitive cells of childhood, and is considered a childhood cancer.

 Research has indicated that there is a chemeric relationship between desmoplastic small round cell tumor and Wilm's Tumor and Ewing's Sarcoma. DSRCT is associated with a unique chromosomal translocation (t11;22)(p13:q12) resulting in a EWS/WTI transcript that is diagnostic of this tumor. This transcript codes for a protein that acts as a transcriptional activator that fails to suppress tumor growth.

Symptoms

 There are few early warning signs that a patient has a desmoplastic small round cell tumor. Patients are often young and healthy as the tumors grow and spread uninhibited within the abdominal cavity. These are rare tumors and symptoms are often misdiagnosed by family physicians. The abdominal masses can grow to enormous size before being noticed by the patient. The tumors can be felt as hard, round masses by palpating the abdomen.

 First symptoms of the disease often include abdominal distention, abdominal mass, abdominal or back pain, gastrointestinal obstruction, lack of appetite, ascites, anemia, and/or cachexia.

 Other reported symptoms include unknown lumps, thyroid conditions, hormonal conditions, blood clotting, kidney or urological problems, testicle, breast, uterine, vaginal, or ovarian masses.

Differentials

 Because this is a rare tumor not many family physicians or oncologists are familiar with this disease. DSRCT in young patients can be mistaken for other abdominal tumors including rhabdomyosarcoma, neuroblastoma, and mesenteric carcinoid. In older patients DSRCT can resemble lymphoma, peritoneal mesothelioma, and peritoneal carcinomatosis. In males DSRCT may be mistaken for Germ Cell or testicular cancer. In females DSRCT can be mistaken for Ovarian cancer. Desmoplastic small round cell tumor shares characteristics with other small round cell cancers including Ewing's Sarcoma, Acute Leukemia, small cell Mesothelioma, Neuroblastoma, Primitive Neuroectodermal Tumor, Rhabdomyosarcoma, and Wilm's tumor.

Pathology

 Pathology reveals well circumscribed solid tumor nodules within a dense desmoplastic stroma. Often areas of central necrosis are present. Tumor cells have hyperchromatic nuclei with increased nuclear/cytoplasmic ratio.

 On immunohistochemistry, these cells have trilinear coexpression including the epithelial marker cytokeratin, the mesenchymal markers desmin and vimentin, and the neuronal marker neuron-specific enolase. Thus, although initially thought to be of mesothelial origin due to sites of presentation, it is now hypothesized to arise from a progenitor cell with multiphenotypic differentiation.

 Treatment

 Desmoplastic small round cell tumor is frequently misdiagnosed. Adult patients should always be referred to a sarcoma specialist. This is an aggressive, rare, fast spreading tumor and both pediatric and adult patients should be treated at a Sarcoma Center.

 There is no standard protocol for the disease. However, recent journals and studies have reported that some patients respond to high dose (P6 Protocol) chemotherapy, maintenance chemotherapy, debulking operation , cytoreductive surgery, and radiation therapy. Other treatment options include: Hematopoietic stem cell transplantation, Intensity-Modulated Radiation Therapy, Radiofrequency ablation, Stereotactic Body radiation therapy, Intraperitoneal hyperthermic chemoperfusion, and Clinical Trials.

  Prognosis

 The prognosis for desmoplastic small round cell tumor remains poor with less than 20% surviving beyond two to three years. Prognosis often depends upon the stage of the cancer and the grade of the tumor. Because the disease can be misdiagnosed or remain undetected tumors frequently grow large within the abdomen and metastasized or seed to other parts of the body.

 There is no known organ or area of origin. Desmoplastic small round cell tumor can metastasize through lymph nodes or the blood stream. Sites of metastatis include the spleen, diaphragm, liver, large and small intestine, lungs, central nervous system, bones, uterus, bladder, genitals, abdominal cavity, and the brain.

 Indications are that a multi-modality approach of high dose chemotherapy, 90-100% surgical resection, radiation, and stem cell rescue improves survival for some patients.

 Some patients with inoperable tumor seem to benefit from long term low dose chemotherapy, turning desmoplastic small round cell tumor into a chronic disease.

  Research

 The Stehlin Foundation currently offers DSRCT patients the opportunity to send samples of their tumors free of charge for testing. Research scientists are growing the samples on nude mice and testing various chemical agents to find which are most effective against the individual's tumor.

 Patients with advanced desmoplastic small round cell tumor may qualify to participate in Clinical Trials that are researching new drugs to treat the disease. Because of the similarities with Ewing's sarcoma patients with desmoplastic small round cell tumor are often eligible for the same Clinical Trials.