Desmoplastic small round cell tumor (DSRCT) is a unique, highly aggressive neoplasm with characteristic topographic, histologic, immunohistochemical, cytogenetic and molecular features. It chiefly affects adolescent males and young adults and is most frequently presented as a large abdominal mass with widespread peritoneal involvement at the time of diagnosis. Histologically, it is composed of nests of small, undifferentiated round or oval hyperchromatic cells embedded in abundant desmoplastic stroma. A multidisciplinary treatment including chemotherapy, aggressive debulking surgery, radiation and myeloablative chemotherapy with stem cell rescue might be the proper approach to treat this rare malignancy and may improve progression-free survival. This book presents current research in the study of the desmoplastic small round cell tumor.