Desmoplastic Small Round Cell Tumor
Image Description
Sharply demarcated tumor nests separated by desmoplastic stroma. Necrosis is seen on the right side of the image.
About the Disease
Desmoplastic small round cell tumor (DSRCT) is a rare highly aggressive tumor of adolescent and young adults with a strong male predominance. It usually involves abdominal or pelvic peritoneum. The tumor is large and multinodular with a firm, gray-white cut surface and areas of hemorrhage, necrosis and cystic change. It is composed of undifferentiated small blue cells arranged in sharply demarcated nests in a background of vascular desmoplastic stroma. Rare cases show significant nuclear atypia and single filing pattern (reminiscent of lobular breast carcinoma) or Homer Wright-like rosettes. Most cases co-express epithelial (cytokeratin AE1/AE3, EMA), mesenchymal (vimentin, desmin - paranuclear dot-like positivity), and neural markers (NSE). WT1 is positive (antibody to carboxy terminus; nuclear expression). DSRCT shows chromosomal translocation t(11:22) (p13; q12) involving the EWSR1 gene (22q12) and WT1 gene (11p13). The translocation results in the expression of a chimeric EWSR1-WT1 protein that acts as a powerful mitogen and permits tumor growth. The EWSR1-WT1 fusion can be detected by RT-PCR or FISH. The differential diagnosis included other small round blue cell tumors. The treatment consists of a combination of extensive debulking procedure, intraperitoneal/systemic chemotherapy, radiotherapy with or without stem cell transplantation. The prognosis is dismal with a 5-yr survival rate of less than 15%.