Desmoplastic Small Cell Tumor in the Pancreas

Abstract

Desmoplastic small cell tumor (DSCT) is a distinct type of small blue cell tumors and is characterized by the unique karyotypic aberration involving the fusion of the Ewing's sarcoma (EWS) gene and Wilms' tumor (WT1) gene. Typically, it grows along serosal surfaces; however, in some cases, the tumor presents as a dominant mass in an internal organ. Examples of DSCT forming a primary mass in ovary, testes, and brain have been described, but its presentation as a primary pancreatic mass has not been reported previously. The case reported here is a 31-year-old woman who presented with a 14-cm mass in the pancreas. There were smaller nodules on the peritoneal surfaces that were regarded clinically as metastasis from a primary pancreatic tumor. During the frozen section, the diagnosis of a poorly differentiated endocrine carcinoma of pancreatic origin was rendered and patient underwent subtotal pancreatectomy. On microscopic examination, the tumor was composed of large nests and broad bands of small blue cells, separated by fibrous stroma. Immunohistochemical stains showed positivity of the tumor cells for cytokeratins (AE1:AE3 and CAM5.2), neuron specific enolase, desmin and WT1, whereas chromogranin, S-100, and CD99 were negative. Since this immunoprofile is characteristic of DSCT, molecular analysis was performed which revealed the presence of EWS-WT1 gene fusion characteristic of DSCT. This case shows that in addition to primary pancreatic tumors characterized by prominent cellularity such as solid pseudopapillary tumors, acinar cell carcinoma, pancreatoblastoma, endocrine tumors, and other small blue cell tumors, the differential diagnosis of cellular, stroma-poor neoplasia in the pancreas also includes DSCT. This case is also another demonstrative example of how DSCT may form a dominant mass in intraabdominal organs.

Soft tissue tumors associated with EWSR1 translocation

“…Originally, described as a predominantly intra-abdominal tumor, a broader distribution has emerged gradually that includes pleura [61] and tunica vaginalis [62]. Extraserous location has been occasionally reported, including parotid gland [63], posterior cranial fossa [64], central nervous system [65], bone and soft tissue [66][67][68], ovary [69], pancreas [70], and kidney [71,72].…”

Nonductal neoplasms of the pancreas

“…Owing to the rarity of poorly differentiated endocrine carcinomas in the pancreas, the possibility of a metastasis from the lung or direct extension from a contiguous site (eg, the ampulla of Vater, where poorly differentiated endocrine carcinomas are more common 90 ) must always be considered. Pancreatic involvement by primitive neuroectodermal tumors 91 and desmoplastic small round cell tumors 92 should also be considered in the differential diagnosis.…”

Rare Neoplasms

“…Histologic features of these neoplasms are highly variable, as they include tumors of vascular origin, primitive neuroectodermal tumor, synovial sarcoma, desmoplastic small round cell tumor [ 25 ], leiomyosarcoma, malignant fi brous histiocytoma, and others. a) Benign Mesenchymal Tumors A large variety of benign soft tissue neoplasms has been described in the pancreas, including several types of vascular tumors such as hemangioendothelioma [ 26 , 27 ], cavernous hemangioma [ 28 ], and hemangioma not otherwise defi ned [ 29 , 30 ].…”