Endolymphatic sac tumor (ELST) is a rare neoplasm arising in the temporal petrous region thought to originate from endolymphatic sac epithelium. It may arise sporadically or in association with Von-Hippel-Lindau syndrome (VHL). The ELST prevalence in VHL ranges from 3 to 16% and may be the initial presentation of the disease. Onset is usually in the 3rd to 5th decade with hearing loss and an indolent course. ELSTs present as locally destructive lesions with characteristic computed tomography imaging features. Histologically, they show papillary, cystic or glandular architectures. Immunohistochemically, they express keratin, EMA, and variably S100 and GFAP. Currently it is recommended that, given its rarity, ELST needs to be differentiated from other entities with similar morphologic patterns, particularly other VHL-associated neoplasms such as metastatic clear cell renal cell carcinoma (ccRCC). Nineteen ELST cases were studied. Immunohistochemistry (18/19) and single nucleotide polymorphism microarray testing was performed (12/19). Comparison with the immunophenotype and copy number profile in RCC is discussed. Patients presented with characteristic bone destructive lesions in the petrous temporal bones. Pathology of tumors showed characteristic ELST morphology with immunoexpression of CK7, GFAP, S100, PAX-8, PAX-2, CA-9 in the tumor cells. Immunostaines for RCC, CD10, CK20, chromogranin A, synaptophysin, TTF-1, thyroglobulin, and transthyretin were negative in the tumor cells. Molecular testing showed loss of 3p and 9q in 66% (8/12) and 58% (7/12) cases, respectively. Immunoreactivity for renal markers in ELST is an important diagnostic caveat and has not been previously reported. In fact, renal markers are currently recommended in order to rule out metastatic RCC although PAX gene complex and CA-9 have been implicated in the development of the inner ear. Importantly copy number assessment of ELST has not been previously reported. Loss of 3p (including the VHL locus) in ELST suggests similar mechanistic origins as ccRCC.
Acta neuropathologica communications. 2018 Oct 19*** epublish ***
Rachel Jester, Iya Znoyko, Maria Garnovskaya, Joseph N Rozier, Ryan Kegl, Sunil Patel, Tuan Tran, Malak Abedalthagafi, Craig M Horbinski, Mary Richardson, Daynna J Wolff, Razvan Lapadat, William Moore, Fausto J Rodriguez, Jason Mull, Adriana Olar
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 171 Ashley Ave, Charleston, 29425, SC, USA., Department of Neurosurgery, Medical University of South Carolina, 171 Ashley Ave, Charleston, 29425, SC, USA., Department of Pathology, Baylor University Medical Center, 3500 Gaston Ave, Dallas, 75246, TX, USA., Genomics Research Department, Saudi Humane Genome Project, King Fahad Medical City and King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia., Department of Pathology and Neurosurgery, Feinberg School of Medicine, Northwestern University, 251 E. Huron St, Chicago, 60611, IL, USA., Department of Pathology, Loyola University Medical Center, 2160 S 1st Ave, Maywood, 60153, IL, USA., Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, 75390, TX, USA., Department of Pathology, Johns Hopkins Hospital, 1800 Orleans St, Baltimore, 21287, MD, USA., Department of Pathology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, 75390, TX, USA., Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 171 Ashley Ave, Charleston, 29425, SC, USA. .