Middle Ear "Adenoma": a Neuroendocrine Tumor with Predominant L Cell Differentiation

Endocr Pathol. 2021 Dec;32(4):433-441. doi: 10.1007/s12022-021-09684-z. Epub 2021 May 27.


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.

Keywords: L cell; Middle ear adenoma; Neuroendocrine tumor.

MeSH terms

  • Adenoma / classification
  • Adenoma / diagnosis*
  • Adenoma / metabolism
  • Adenoma / pathology
  • Adult
  • Aged
  • Animals
  • Cell Differentiation
  • Diagnosis, Differential
  • Ear Neoplasms / classification
  • Ear Neoplasms / diagnosis*
  • Ear Neoplasms / metabolism
  • Ear Neoplasms / pathology
  • Ear, Middle / metabolism
  • Ear, Middle / pathology*
  • Female
  • Humans
  • Immunohistochemistry
  • L Cells / metabolism
  • L Cells / pathology
  • L Cells / physiology*
  • Male
  • Mice
  • Middle Aged
  • Neuroendocrine Tumors / classification
  • Neuroendocrine Tumors / diagnosis*
  • Neuroendocrine Tumors / metabolism
  • Neuroendocrine Tumors / pathology
  • Retrospective Studies
  • Terminology as Topic