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17 April 2014 - Case of the Week #349

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Thanks to Dr. Koteeswaran Govindaswamy, Mahatma Gandhi Medical College and Research Institute (India), for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.



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Case of the Week #349

Clinical History:
A 45 year old man presented with noise in his left ear and mild hearing loss for one year He was diagnosed clinically with a pulsating tinnitus. A MRI of the temporal bone showed a well defined soft tissue mass in the left middle ear cavity involving the meso- and hypo-tympanus and encasing the middle ear ossicle. A mastoidectomy was performed.

Gross description:
Soft dark tan nodules in aggregate measuring 6 mm.

HPE:
Micro images:

H&E images



What is your diagnosis?































Diagnosis:
Glomus tympanicum

Discussion:
Histology showed a neoplasm resembling a capillary hemangioma, composed primarily of variable sized capillary channels lined by a single layer of endothelial cells. An adjacent area was solid with closely packed small nests of round to epithelioid cells surrounded by capillaries. There were no mitoses.

Immunostains were obtained:

S100

VEGF



S100 showed no definite sustentacular cells, likely obscured by capillaries. VEGF showed staining of vessels, but no staining of most tumor cells.

Glomus tympanicum, also called jugulotympanic paraganglioma, is the most common tumor of the middle ear, usually occurring in women ages 40-69 years (eMedicine). Most arise in the jugular bulb, causing a mass in the middle ear or external auditory canal. The remainder arise from the tympanic branch of the glossopharyngeal nerve, causing a middle ear mass, or the posterior auricular branch of the vagus nerve, causing an external auditory canal mass. They usually cause a conductive hearing loss, and may be locally invasive into the temporal bone and mastoid, causing cranial nerve palsies, cerebellar dysfunction, dysphagia or hoarseness.

Histologically, they have the classic organoid (zellballen) or nesting pattern of paragangliomas with central round/oval chief cells containing abundant eosinophilic granular or vacuolated cytoplasm and uniform nuclei with dispersed chromatin. Although difficult to identify in this case, sustentacular cells (spindled and basophilic) are usually present at the periphery of nests, which are separated by a fibrovascular stroma. Tumors typically have benign features, but may have pleomorphism, dense fibrous stroma or apparent infiltration. Mitoses and necrosis are rare.

The chief cells in the tumor are immunoreactive for chromogranin and synaptophysin, and typically the sustentacular cells are S100+. Reticulin stains the stroma and delineates the nesting pattern, which is particularly helpful with crushed specimens.

The differential diagnosis includes capillary hemangioma (Case Rep Otolaryngol 2012;2012:305172), which lack the organoid pattern and cellular composition (chief and sustentacular cells) of paragangliomas.

Common treatment options are surgery (Otolaryngol Head Neck Surg 2015;152:136, Auris Nasus Larynx 2010;37:661), which may be accompanied by profuse bleeding (Skull Base 2011;21:309) or radiosurgery / gamma knife (J Neurosurg 2014;121 Suppl:198), with low complication rates despite the location. There is a low recurrence rate, and occasional cases may have malignant behavior with metastases.

Nat Pernick, M.D., President
and Shivani Thakore, Associate Medical Editor
PathologyOutlines.com, Inc.
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Bingham Farms, Michigan (USA) 48025
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