[1190] Middle Ear Adenomas Contain Focal Areas with Basal Cells but Not Myoepithelial Cells.

Abberly Lott Limbach, Aaron P Hoschar, Deborah J Chute. Cleveland Clinic, OH

Background: Middle ear adenomas (MEAs) are rare neoplasms generally considered to be benign. The true nature of these neoplasms is unknown but are considered to be along a spectrum with carcinoid tumors. To date, immunohistochemical staining for myoepithelial markers has not been reported in these lesions.
Design: The archives of one institution were retrospectively searched for tumors arising within the middle ear which had material available for immunohistochemical staining. Six cases of MEA and four cases of jugulotympanic paraganglioma (JTG) were identified. An additional two cases of ceruminous adenoma were included for comparison. Immunohistochemical staining was performed for the following markers: smooth muscle actin, p63, S100 protein, cytokeratin 5/6, and cytokeratin 7. The pattern of immunohistochemical staining within each tumor was recorded as negative (<1% of cells), focal (<25% of cells) or diffuse (>25% of cells), and sub-classified as luminal or abluminal where appropriate.
Results: The MEAs showed a range of morphologic patterns including cribriform, trabecular, nested and/or glandular architecture. Crush artifact was common in all biopsies. Immunohistochemical staining was focally to diffusely positive for CK7 in all cases, with accentuation in areas with glandular architecture. CK 7 was positive in a predominantly luminal pattern in the glandular areas. The abluminal cells were focally positive for CK5/6 and p63 in the glandular areas. S100 was focally positive in one case, and the MEAs were uniformly negative for SMA. JTGs displayed lobulated nests of cells centered on vascular structures. Immunohistochemical staining was diffusely positive for S100 with accentuation of sustentacular cells, and CK7, CK5/6, SMA and p63 were uniformly negative. Ceruminous adenomas showed gland formation with eosinophilic luminal secretions. Immunohistochemical staining for CK7 was diffusely positive in a luminal pattern, and CK5/6, p63, S100, and SMA were diffusely positive in the abluminal cells.
Conclusions: The immunohistochemical profile of MEAs suggests that these tumors harbor at least 2 cell populations, including luminal and basal cells, albeit focal. However, unlike ceruminous adenomas, MEAs lack true myoepithelial differentiation given the absence of S100 and SMA staining in all cases.
Category: Head & Neck

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 157, Monday Morning


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