Atypical mature bone in the otosclerotic otic capsule as the differentiated zone of an invasive osseous neoplasm

Abstract

Conclusion: A large proportion of the mature otic capsule bone in cases of otosclerosis lies in plaques in direct contiguity with active otosclerosis and, because it shows significant structural defects, it should be regarded as part of the otosclerotic process. These appearances support our previously described suggestion that otosclerosis is an invasive osseous neoplasm, the mature atypical bone representing differentiation of earlier-formed invasive neoplastic osseous tissue. Objectives: We sought structural features in differentiated bone within the otic capsules of cases of otosclerosis that might indicate a relation to the underlying disease process. Methods: Fifty temporal bones from 42 adult patients with otosclerosis were processed into stained histological sections and the appearance of the otic capsule was compared with that of the same tissue, processed in the same way, in 10 cases that did not show otosclerosis. Results: In the cochlear otic capsules of otosclerotic temporal bones, when traced back along the otosclerotic plaque from the invasive front, atypical shapes and arrangements of osteons were seen, often with otospongiosis (severe dilatation of multiple Volkmann's canals), culminating in larger differentiated osteons with irregularities in structure. In the medial region of the otosclerotic cochlear otic capsule, at a similar position to that where giant normal osteons are present in the normal temporal bone, differentiated, giant abnormal osteons were seen. In the otosclerotic vestibular otic capsule there were changes similar to those of the otosclerotic cochlea (apart from the giant osteons) and many osteons composed of clusters of atypical osteoblast-like cells around highly atypical Volkmann's canals.

Keywords::

• Osteons
• Volkmann's canals
• globuli ossei
• invasive front
• stapedectomy
• otospongiosis
• microslicing
• tissue culture

Acknowledgments

Dr Fred Linthicum, Director of the Temporal Bone Pathology Department at the House Research Institute, Los Angeles, has again been extremely helpful to us in our work in his department. Ms Ana Cordero, Histologist, House Research Institute, provided much expert assistance. Mr Bob Chapman, Senior Scientist, Department of Histopathology, Charing Cross Hospital, London, continues to guide us at every step of our microphotographic representations. Some financial support for the work carried out was provided by the Shrier Audiology Research Fund, Imperial College, London, UK.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.