Middle ear and inner ear tumors - malignant

Endolymphatic sac tumor

Last author update: 1 October 2013
Last staff update: 1 March 2021

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PubMed Search: Endolymphatic sac tumor [pathology]

Nat Pernick, M.D.
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Cite this page: Pernick N. Endolymphatic sac tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/earendolymphaticsac.html. Accessed June 8th, 2023.
Definition / general
  • Uncommon, associated with von Hippel-Lindau syndrome (11% have these tumors) and female adnexal tumor of presumed wolffian origin (Am J Surg Pathol 1994;18:1254); also somatic mutations of VHL gene in non VHL patients (Cancer Res 2000;60:5963)
  • Most arise within intraosseous portion of the endolymphatic duct / sac, with precursor lesions present in VHL patients (Cancer Res 2005;65:10847)
  • Median age 30s, range of 11 - 71 years
  • Symptoms: early sensorineural hearing loss, tinnitus and episodic vertigo
  • The 2017 WHO now separates aggressive papillary tumor from endolymphatic sac tumor
  • Also called papillary adenoma of endolymphatic sac / temporal bone, adenocarcinoma of temporal bone / mastoid, low grade adenocarcinoma of probable endolymphatic sac origin, Heffner tumor
Radiology description
  • Tumor in posterior medial petrous ridge of temporal bone (site of endolymphatic sac)
Case reports
  • Radical surgery including mastoidectomy and temporal bone resection with possible loss of cranial nerves
  • Tumor grows slowly with only one reported metastasis (J Neurosurg Spine 2005;3:68) but may recur with inadequate excision
  • Is infiltrative, destructive and may cause death
  • Bleeds profusely at surgery
Microscopic (histologic) description
  • Simple papillary structures composed of single layer of columnar to cuboidal epithelium, often with distinct cell boundaries
  • May have apparent myoepithelial layer that actually is flattened stroma; epithelial cells have pale-clear cytoplasm, uniform central or luminal nuclei
  • Often granulation tissue reaction with small vascular spaces and mixed inflammatory infiltrate is present next to tumor cells
  • Occasional thyroid like hypercellular areas with cystic glandular spaces containing colloid like material
  • May have areas of recent hemorrhage with cholesterol clefts
  • Minimal pleomorphism
  • No / rare mitotic figures or necrosis
  • Resembles choroid plexus papilloma
Microscopic (histologic) images

Contributed by Kelly Magliocca D.D.S., M.P.H.

Endolymphatic sac tumor, 2x

Endolymphatic sac tumor, 5x

Endolymphatic sac tumor, 15x

Endolymphatic sac tumor, 20x

Endolymphatic sac tumor, 40x

CAIX, 20x

PAX8, 40x

Negative RCC, 20x

Negative CD10, 20x

Images hosted on other servers:
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Various images

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Papilla with hemorrhagic material

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Papilla with vacuolated cells and colloid-like material

Cytology description
  • Rare epithelial cell clusters, some with papillary features
  • Foamy macrophages
  • Epithelial cells have eosinophilic and focally vacuolated cytoplasm, some with pigmented granules resembling hemosiderin, well defined cell borders, bland nuclei
Positive stains
Negative stains
Electron microscopy description
  • Intercellular junctional complexes, microvilli, basement membrane, rough ER, glycogen, secretory granules
Differential diagnosis

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