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Middle Ear "Adenoma": a Neuroendocrine Tumor with Predominant L Cell Differentiation
Sylvia L Asa1, Knarik Arkun2, Arthur S Tischler2
1Department of Pathology, University Hospitals Cleveland Medical Center, Case Western Reserve University, Cleveland Ohio, 44106, USA. Pathlady01@gmail.com.
Insights
Middle ear adenomas are reclassified as well-differentiated neuroendocrine tumors (NETs) resembling hindgut NETs. This finding aids in distinguishing middle ear NETs from paragangliomas using specific L cell markers.
Area of Science:
- Otolaryngology
- Endocrinology
- Surgical Pathology
Background:
- Tumors historically termed "middle ear adenomas" lack definitive classification.
- Understanding the cellular origin and classification of middle ear neoplasms is crucial for accurate diagnosis and treatment.
- Neuroendocrine tumors (NETs) are a diverse group of neoplasms with varying differentiation and origin.
Purpose of the Study:
- To re-evaluate the nature of "middle ear adenomas" using advanced morphological and immunohistochemical techniques.
- To determine the cellular lineage and potential origin of these middle ear tumors.
- To establish an immunohistochemical profile for differential diagnosis of middle ear neoplasms.
Main Methods:
- Morphological analysis of tumor tissues.
- Immunohistochemical staining for neuroendocrine markers, keratins, and specific L cell markers (glucagon, pancreatic polypeptide, PYY, SATB2).
- Comparison of tumor cell markers with those in normal middle ear epithelium.
Main Results:
- "Middle ear adenomas" are identified as well-differentiated epithelial neuroendocrine tumors (NETs).
- These tumors exhibit expression of intestinal L cell markers (glucagon, pancreatic polypeptide, PYY, SATB2), similar to hindgut NETs.
- Normal middle ear epithelium also expresses these L cell markers, suggesting a common cellular origin.
Conclusions:
- "Middle ear adenomas" are reclassified as epithelial neuroendocrine tumors (NETs) of the middle ear, resembling hindgut NETs.
- The established immunohistochemical profile, including L cell markers and SATB2, is valuable for differentiating these NETs from other middle ear neoplasms like paragangliomas.
- The presence of neuroendocrine cells in normal middle ear mucosa warrants further investigation into middle ear physiology and pathology.
Abstract:
This morphological and immunohistochemical study demonstrates that tumors currently known as "middle ear adenomas" are truly well-differentiated epithelial neuroendocrine tumors (NETs) composed of cells comparable to normal intestinal L cells, and therefore, these tumors resemble hindgut NETs. These tumors show consistent expression of glucagon, pancreatic polypeptide, PYY, and the transcription factor SATB2, as well as generic neuroendocrine markers and keratins. The same L cell markers are expressed by cells within the normal middle ear epithelium. These markers define a valuable immunohistochemical profile that can be used for differential diagnosis of middle ear neoplasms, particularly in distinguishing epithelial NETs from paragangliomas. The discovery of neuroendocrine cells expressing the same markers in non-neoplastic middle ear mucosa opens new areas of investigation into the physiology of the normal middle ear and the pathophysiology of middle ear disorders.
