Endolymphatic sac tumor

Case contributed by A.Prof Frank Gaillard


Uncertain cause for initial imaging.

Patient Data

Age: 65 years

On the left, the posterior part of the vestibular aqueduct and adjacent bone are eroded. 


Best seen on axial T1 with contrast is an extra-axial mass located at the expected location of the left endolymphatic sac (posterior aspect of the petrous bone). It is lobulated and vividly enhancing with erosion of the adjacent bone. Inferiorly it involves but does not occlude the sigmoid sinus. 

Conclusion: given the location and erosion of bone an endolymphatic sac tumor is favored. 

Case Discussion

The patient went on to have resection.


The sections show a moderately cellular tumor. It forms elongated nests and acinar-like structures. Some contain calcific deposits and psammoma bodies. The tumor cells have round nuclei, inconspicuous nucleoli and moderate amounts of 'oncocytic type' eosinophilic cytoplasm.

The tumor cells are CAM5.2, AE1/3, CK7, EMA, S-100 and SOX-10 positive. Progesterone receptor, melan-A, synaptophysin, TTF-1 and thyroglobulin are negative.

The PAS stain shows no fungi. The Ziehl-Neelsen stain shows no acid-fast bacilli. Though the architecture is not quite papillary but given the immunoprofile and the site, the features are consistent with papillary tumor of the endolymphatic sac.

FINAL DIAGNOSIS: Papillary tumor of the endolymphatic sac.

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Case information

rID: 59140
Published: 7th Jun 2018
Last edited: 16th Jul 2018
Inclusion in quiz mode: Included

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