Microscopic description and IHC:

Unencapsulated and infiltrative growth. The neoplasm shows glandular, trabecular and focally solid architecture. The nuclei are excentrically placed and round to oval (plasmacytoid). No necrosis, mitosis or marked pleomorphism. Perineural/lymphovascular invasion is absent. Ducts show dual cell population: inner, flattened eosinophilic cells and basal, cuboidal-columnar cells.

Immunohistochemical features:
  • AE 1/3: (+)
  • Synaptophysin: (+)
  • CK7: (+) luminal cells within glandular spaces
  • P63: (+) basal layer
  • SMA: (-)
  • Chromogranin: (-)

Discussion:

Middle ear adenoma is a benign glandular neoplasm showing both neuroendocrine and mucin-secreting differentiation.

It is the most common tumor of the middle ear with an average age of presentation at 45 years and equal gender distribution.

Unilateral hearing loss, tinnitus and ear discharge are the most common presenting symptoms.

Facial nerve paralysis or paresthesia may be due to mass effect rather than invasion of nerves.

Complete excision, including ossicular chain to prevent recurrence, is the treatment of choice.

Head CT shows middle ear mass with intact tympanic membrane and no finding of chronic otitis media.

References:

Thompson, L. D., MD, & Wenig, B. M., MD. (2012). Diagnostic Pathology Head and Neck (1st ed.). Altona, Canada: Amirsys.

Goldblum, J. R. (2013). Head and Neck Pathology (2nd ed., Foundations in Diagnostic Pathology). Philadelphia, PA: Elsevier Saunders.

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