Morphological Evidence for the Sensitivity of the Ear Canal of Odontocetes as shown by Immunohistochemistry and Transmission Electron Microscopy.

The function of the external ear canal in cetaceans is still under debate and its morphology is largely unknown. Immunohistochemical (IHC) analyses using antibodies specific for nervous tissue (anti-S100, anti-NSE, anti-NF, and anti-PGP 9.5), together with transmission electron microscopy (TEM) and various histological techniques, were carried out to investigate the peripheral nervous system of the ear canals of several species of toothed whales and terrestrial Cetartiodactyla. This study highlights the innervation of the ear canal with the presence of lamellar corpuscles over its entire course, and their absence in all studied terrestrial mammals. Each corpuscle consisted of a central axon, surrounded by lamellae of Schwann receptor cells, surrounded by a thin cellular layer, as shown by IHC and TEM. These findings indicate that the corpuscles are mechanoreceptors that resemble the inner core of Pacinian corpuscles without capsule or outer core, and were labelled as simple lamellar corpuscles. They form part of a sensory system that may represent a unique phylogenetic feature of cetaceans, and an evolutionary adaptation to life in the marine environment. Although the exact function of the ear canal is not fully clear, we provide essential knowledge and a preliminary hypothetical deviation on its function as a unique sensory organ.

Leiomyoma of the External Auditory Canal.

Angioleiomyomas (ALMAs) are benign tumors that arise from smooth muscle cells that form the tunica media of vascular structures. To our knowledge, only five cases of ALMA of the external auditory canal (EAC) have been reported. We report the case of a 52-year-old man with left otalgia, otorrhea, auricular fullness, and hearing loss. On otomicroscopic examination, a reddish and smooth mass completely occluding the EAC was seen. Computed tomography scan showed a soft tissue mass with a complete opacification of the left EAC. A possible diagnosis of ALMA should be considered when finding a tumor inside the external ear canal. An accurate pathological examination should be performed to differentiate benign vascular ALMA from malignant leiomyosarcomas. Complete surgical excision is the treatment of choice in benign tumors.

Human ceruminous gland: ultrastructure and histochemical analysis of antimicrobial and cytoskeletal components.

The ceruminous glands in the skin of the human external auditory canal are modified apocrine glands, which, together with sebaceous glands, produce the cerumen, the ear wax. Cerumen plays an important role in the protection of the ear canal against physical damage and microbial invasion. We studied the morphology of the glandular cells by light and electronmicroscopy. Antimicrobial and cytoskeletal components of the ceruminous glands were investigated by immunohistochemical methods. Numerous antimicrobial proteins and peptides are present in the ceruminous glandular cells: beta-defensin-1, beta-defensin-2, cathelicidin, lysozyme, lactoferrin, MUC1, secretory component of IgA. These data indicate a crucial role in the innate host defense against diverse pathogens. The apocrine secretion mechanism is a special mode of secretion by which the apical part of the cell cytoplasm surrounded by a membrane is pinched off. We could show that the presence of actin filaments, CK 19 and CK 7, seems to play a role in the pinching-off mechanism. Finally, we showed the secretion of lipid vesicles from the ceruminous gland. We could extend the number of detected antimicrobial peptides and proteins in human ceruminous glandular cells that protect the surface of the external auditory meatus. In addition, we detected proteins involved in the apocrine secretion mode of the ceruminous gland.

Argyrophilic nucleolar organizer regions in auditory meatal skin and middle ear cholesteatoma.

Comparative silver-staining of argyrophilic nuclear organizer regions (AgNORs) was performed to study the proliferative activity of auditory meatal skin and middle ear cholesteatoma. AgNOR expression patterns were counted by standardized methods in two centres, Bochum and London, and mean numbers of dots per nucleus were calculated. Specimens of normal auditory meatal skin showed 1.54 dots/nucleus (n = 12) in the Bochum study, whereas cholesteatoma had 3.71 dots/nucleus (n = 21). In the London study normal meatal skin showed two dots/nucleus (n = 4), whereas acquired cholesteatoma (n = 8) gave a mean of 4.90 dots/nucleus and congenital cholesteatoma a mean of 4.70 dots/nucleus (n = 2). Our findings confirm the hyperproliferative state of middle ear cholesteatoma, suggest that the congenital variety of cholesteatoma may have a similar activity and indicate that AgNOR staining is a useful technique for assessing cellular proliferation in cholesteatoma and objectifying and quantifying its aggressive behaviour.

Auditory epidermal cell migration. V. Transmission electron-microscopic study of tympanic membrane and external auditory canal in the mouse.

The morphology of the tympanic membrane (TM) and external auditory canal (EAC) in mice was examined by transmission electron microscopy, in seven different regions: the handle of the malleus (HM) region, the intermediate and annular regions of the pars tensa (PT), the region of the pars flaccida (PF), the annular and osseous regions of the EAC and the cartilaginous region of the EAC. Each region displayed its own unique findings. In most regions of the TM and EAC-except the intermediate region of the PT-basal layer cells formed cytoplasmic processes (CPs) on their basal surface and adhered to the basement membrane (BM) by means of hemidesmosomes (HDs). This observation may suggest the presence of stem cells. In contrast, basal cells in the intermediate region of the PT did not extend any CPs from the basal surface but attached to the BM by a few characteristic spots of HD-like density but lacking the characteristics of HDs. It is concluded that stem cels are not present there and that basal cells connect loosely with the BM, thus providing the necessary morphological conditions to migrate laterally toward the annular region. The outermost layer of the epidermis in the annular region of the EAC showed numerous cytoplasmic projections (so-called 'finger-like projections'), representing keratinization and desquamation of epidermal cells (keratinocytes). These projections are believed to be the terminal differentiation of epidermal cells originating from the general centre in the HM region of the PT. The epidermis of the PF is an extension of the upper wall of the EAC, but the two regions differ morphologically.

Monostotic fibrous dysplasia of the temporal bone with associated lymphadenopathy.

Fibrous dysplasia of the temporal bone is a very unusual condition and its association with an abnormal lymph node has not been previously reported. Although it is benign condition causing conductive deafness, cholesteatoma may develop insidiously as illustrated by this case. We recommend regular long term follow up and surgical exploration if a changing clinical picture suggests the possibility of complications.

Effect of vitamin A on the growth and differentiation of rat external auditory canal epithelium in organ culture.

Intact rat external ear canal explants were maintained either in retinoid-deficient or retinoid-supplemented medium for 7, 10, 14, and 21 days. The morphology of the external ear canal epidermis was well maintained, including the presence of sebaceous glands even after 21 days in culture with retinoid-deficient medium. However, after culturing in retinoid-supplemented medium, the external ear canal epithelium showed both a loss of keratohyalin granules and the formation of keratin. Extensive microvilli formation occurred, even though the desquamation process continued from the superficial layer after 7, 10, and 14 days in culture with retinoid-enriched medium. After 21 days in culture with retinoid-supplemented medium, the ear canal epithelium contained well-developed Golgi apparatus and secretory granules as well. It was concluded that the ear canal epithelium was transformed into a secretory-like mucosal epithelium by retinoid supplementation.

Pleomorphic adenoma of the external auditory canal. An immunohistochemical and ultrastructural study.

Primary tumors arising from the glandular structures of the external auditory canal (EAC) are rare, with the majority arising from the ceruminous glands. The histochemical, immunohistochemical, and electron microscopic features of a pleomorphic adenoma of the EAC are presented; this is the seventh case reported. These studies confirm the key role of the myoepithelial cell in this tumor and include a correlation with pleomorphic adenomas in other sites.

Neurothekeoma (peripheral nerve sheath myxoma) of the external auditory canal.

A patient who presented with an isolated soft-tissue tumor in the lateral portion of the external auditory canal, which after removal was diagnosed histopathologically as a peripheral nerve sheath neurothekeoma, is presented. Peripheral nerve sheath myxomas (neurothekeomas or perineural myxomas) have been reported to occur on the central area of the face, arms and shoulders. This is the first case in which a tumor of this type has been reported to develop in the external auditory canal. The distinguishing histopathological characteristics and the differential diagnosis of this tumor are discussed.

Corneocyte architecture in the human external auditory canal.

Using skin dissected from the external auditory canals of fresh cadaveric temporal bones, the structure of the stratum corneum was investigated by the techniques of alkaline expansion of cryostat sections, silver staining of epidermal sheets, and scanning electron microscopy. Ordered epidermal column formation was observed in the stratum corneum from skin obtained from both the bony and cartilaginous portions of the canal. Occasionally, in areas of skin where the stratum corneum was considerably thickened, this vertical organization was lost, and the corneocytes randomly arranged. This orderly cellular architectural arrangement is a feature of the non-migratory skin of lower mammals, and has also been reported to occur in some areas of human skin. The functional relevance of this finding in the skin of the external canal is that the whole of the stratum corneum must migrate as one in order to preserve a regular vertical structure, suggesting that epidermal migration occurs in the deeper layers of the meatal epidermis.

Morphological differences between secretory cells of wet and dry types of human ceruminous glands.

Morphological differences between secretory cells of the wet and dry types of human ceruminous glands were examined. The heights of secretory cells varied from tall and medium to low in both wet- and dry-type glands. The two gland types differed in morphologic features of the tall cells and the cells of medium height. The Golgi apparatus was well developed in the tall cells and fairly well developed in the cells of medium height in the wet-type gland, whereas it was generally small in the corresponding cells of the dry type. Light granules were abundant in the tall cells and in the cells of medium height in the wet-type gland, whereas light granules were rare in these cells in the dry-type gland. Furthermore, the light granules in the wet-type gland cells were observed in close relation to a well-developed Golgi apparatus, and sometimes showed a morphologic appearance suggesting exocytosis. Apical protrusions, probably related to apocrine secretion, were generally large and round and bore "microvilli and light granules" or "very few microvilli and no light granules" in the tall cells of the wet-type gland. However, the protrusions of the tall cells of the dry-type gland were generally large and slender and possessed no microvilli and no granules. The protrusions were not observed in the cells of medium height or in low cells in either type of gland. The results show that eccrine secretion characterizes the wet-type gland, but it is not clearly evident in the dry-type gland. This differences may be related to differences in composition between the wet and dry cerumens.

An ultrastructural study of the skin of the tympanic membrane and external ear canal of the guinea pig.

The ultrastructure of the skin covering the tympanic membrane and external ear canal has been studied in eight guinea pigs, to identify any features which could be related to the rapid movement of the epidermal surface at this site. Migratory epidermis showed evidence of reduced intercellular adhesion in the deeper layers and reduced differentiation in all layers. Differentiation was more evident in cell ridges found at the junctional zone between migratory and non-migratory skin. The findings agree with those of previous authors, and indicate that migration is most likely to occur within the deeper layers of the epidermis.

The formation of ultrastructural epithelial and subepithelial connective tissue changes in experimentally induced cholesteatomas in guinea pigs.

Histoacryl-induced cholesteatomas were produced in guinea pigs at the posterosuperior part of the external ear canal adjacent to the tympanic membrane. Semithin and ultrathin tissue sections were used to study primary formation of the cholesteatoma as well as the influence of the altered epithelium upon the bordering zone of connective tissue. Quantitative and qualitative tissue changes were analyzed by electron microscopy and showed degradation and new formation of collagen and activation of fibroblasts. Our findings are similar to those previously reported on human cholesteatomas and indicate that the bordering subepithelial tissue seems to be influenced through the basilar membrane.

Osteomas and exostoses of the external auditory canal - medical and surgical management.

Osteomas and exostoses have distinct clinical and histopathologic features. Osteomas are usually solitary, pedunculated, bony growths attached to the tympanosquamous or tympanomastoid suture line, characterized histologically by an internal structure of abundant discrete fibrovascular channels surrounded by irregularly oriented lamellated bone. Exostoses are usually multiple, bilaterally symmetrical, broad based elevations of bone involving the tympanic bone. They are histologically characterized by parallel, concentric layers of subperiosteal bone. The infrequent symptoms resulting from these lesions can usually be managed medically; however, on occasion surgical removal is indicated. While surgical removal of the osteoma is usually possible via the external auditory meatus, we recommend that an exostosis be removed utilizing a postauricular approach.

Secretory mechanisms of human ceruminous glands: a transmission and scanning electron microscopic study.

Two secretory mechanisms (eccrine and apocrine) were observed by transmission and scanning electron microscopy in the same secretory cells of the human ceruminous glands. The eccrine secretion occurs as a typical exocytosis by fusion of the limiting membrane of the secretory granule with the apical plasmalemma. The apocrine secretion is more complex and takes place by sequential steps: bulging of the cellular apex into the lumen, constriction of the projection, and detachment of it from the cell. This mechanism generally causes the removal of the entire projection all at once by decapitation at its base; some variations of this process have been found, however, and are described in the present work. A double membrane, apparently separating the apical protrusion from the rest of the cell, is noticeable in our photographs. Nevertheless, even if this membrane is very similar to a demarcation layer, we consider it as an intercellular double membrane separating two obliquely sectioned cells.

Osteomas and exostoses of the external auditory canal. A clinical, histopathologic and scanning electron microscopic study.

Osteomas of the external auditory canal are considered clinically to be discrete, pedunculated bone lesions arising along the tympanosquamous suture. They are benign lesions but often are slowly progressive in size. Exostoses of the external auditory canal are broad-based elevations of bone usually multiple and bilaterally symmetric, involving the tympanic bone. It appears that both clinical and histopathologic evidence is sufficient to justify the impression that these two lesions should be considered separate entities and clinical diagnostic and histopathologic criteria have been suggested for diagnosis of these lesions.