Primitive Neuroectodermal Tumors of the Biliary and Gastrointestinal Tracts: Clinicopathologic and Molecular Diagnostic Study of Two Cases

Abstract

Primitive neuroectodermal tumor (PNET) is a prototypic malignant small round cell tumor of childhood that is characterized in most cases by t(11;22) resulting in an EWS-FLI1 gene fusion. Once thought to be uncommon, PNET now accounts for almost 20% of malignant soft tissue tumors in children. Increased recognition of PNET is partly due to advances in immunohistochemistry and molecular diagnostics, which have led to the identification of the tumor in non-classical sites. We report the clinical, histologic, immunohistochemical, and molecular findings of two visceral PNETs of the digestive system--one involving the small intestine and the other involving the hepatic duct. Histologically, each tumor was composed of malignant small cells growing in sheets, nests, and lobules; the tumor cells of both cases showed characteristic immunoreactivity for vimentin and O13 (CD99). Reverse transcription-polymerase chain reaction (RT-PCR) analysis for t(11;22) using nested primers was performed with RNA extracted from paraffin-embedded, formalin-fixed tissue and demonstrated an EWS exon 7 to FLI1 exon 5 fusion in both cases, confirmed by Southern blot hybridization and DNA sequence analysis. These results illustrate the expanded clinicopathologic profile of PNET, and demonstrate that visceral PNETs, despite their unusual sites of presentation, maintain the characteristic immunohistochemical and genetic features of PNETs at more conventional sites.

Primitive Neuroectodermal Neoplasia in Coho Salmon, Oncorhynchus kisutch

“…9 In humans, these neoplasms have a histologic appearance similar to the neoplasm described here, with the exception of the rosette or pseudorosette formation being observed in some cases. These neoplasms are commonly positive for vimentin and S-100 protein as well as neuron-specific enolase.…”

Pediatric liver tumors and hepatic ontogenesis: Common and distinctive pathways

“…In contrast to the kidney, PNET are rare in the hepatobiliary system. In a PNET of the common hepatic duct occurring in a 14-year-old female patient, a clear cell component was noted, and this tumor was CD99-and vimentin-positive, and exhibited an EWS-Fli-1 fusion [108]. The cellular origin of PNET in this location has not yet been clarified, but neural crest-derived cells are candidates.…”

Pathology of Pediatric Gastrointestinal and Liver Disease

“…Isolated case reports of small bowel peripheral neuroectodermal tumor (PNET) (Graham et al 2002 ;Sarangarajan et al 2001 ), gastric malignant schwannoma (Bees et al 1997 ), gastric clear cell sarcoma (Lagmay et al 2009 ), gastric plexiform fi bromyxoma (Miettinen et al 2009b ), esophageal synovial sarcoma a b c Fig. 8.29 Histologic appearance of polypoid ganglioneuroma (same case as Fig.…”