WWTR1-CAMTA1 Fusion Product: A Unique Marker of Epithelioid Hemangioendothelioma
Swanson B David, Nithila N Perinban, Rita A Kandel, Brendan C Dickson. Mount Sinai Hospital, Toronto, ON, Canada
Background: Epithelioid haemangioendothelioma (EHE) is an endothelial neoplasm exhibiting an unusual morphology, and features that occasionally result in diagnostic confusion. The recent discovery of the WWTR1-CAMTA1 gene fusion in EHE confirmed this to be a distinct entity. The purpose of this project was to perform an institutional review of vascular lesions diagnosed as EHE and to assess the presence and specificity of the WWTR1-CAMTA1 fusion product using formalin-fixed paraffin-embedded tissue.
Design: A retrospective review was performed for recent cases of epithelioid haemangioendothelioma, epithelioid haemangioma (EH) and epithelioid angiosarcoma (EAS) diagnosed at our institution. Two cases each of haemangioma and cutaneous angiosarcoma served as negative controls. Ribonucleic acid (RNA) was extracted from archival formalin-fixed, paraffin-embedded tissue and reverse transcriptase-polymerase chain reaction (RT-PCR) was performed using primers specific for the breakpoint between exon 4 of WWTR1 and exons 8 and 9 of CAMTA1.
Results: A total of 7 EHE, 1 EH and 5 EAS were identified. Three cases of EHE were found to contain the WWTR1-CAMTA1 fusion product, 1 case was negative and 1 was inconclusive. RNA could not be obtained from 3 cases. The negative case was noted to contain unconventional histological features. All EH and EAS cases were negative for the fusion product, as were the hemangioma and angiosarcoma.
Conclusions: We confirm the specificity of the WWTR1-CAMTA1 in the diagnosis of EHE using formalin-fixed paraffin-embedded tissue. While one case was negative, the morphology differed somewhat from conventional EHE raising the possibility of an alternative sub-classification. These findings confirm (i) the diagnostic utility of this PCR-based assay in formalin-fixed paraffin-embedded tissue, and (ii) that epithelioid haemangioendothelioma represents a distinct pathologic entity.
Category: Bone & Soft Tissue
Monday, March 4, 2013 1:00 PM
Poster Session II # 2, Monday Afternoon