Neuroendocrine adenoma of the middle ear with extension into the external auditory canal

Summary

We report a case of middle ear adenoma (neuroendocrine adenoma of the middle ear) protruding into the external ear canal. The patient was a 65-year-old man with hearing alterations and a headache in whom an otoscopy disclosed a sessile, pea-sized, brown-reddish, focally bleeding mass located in the posterior-superior aspect of the right external auditory canal. Histopathologically, there was a neoplasm composed of closely packed, sometimes back-to-back glandular structures formed by small uniform cuboidal or cylindrical cells. Small solid islands were also present. Following the histopathologic examination, a high resolution computed tomography was performed showing an extensive osteolytic defect mostly involving the mastoid air cells of the mastoid process with a partial destruction of the middle ear cavity. This defect was filled with a mass-like lesion with the density of soft tissue which bulged to the external auditory canal. Histopathologic examination of the mass in the middle ear cavity revealed findings identical to those seen in the original biopsy, confirming diagnosis of middle ear adenoma extending into the external ear canal.

Keywords:
skin – external auditory canal – neuroendocrine adenoma of the middle ear – carcinoid tumor

Middle ear adenoma (neuroendocrine adenoma of the middle ear) is a rare benign neoplasm arising anywhere in the middle ear cavity, sometimes extending into the mastoid (1). We report a case of middle ear adenoma protruding into the external ear canal as the first sign of the disease.

Case report

A 65-year-old man was referred to an otolaryngologist because of hearing alterations in his right ear and a headache. On otoscopy, a sessile, pea-sized, brown-reddish, focally bleeding mass was identified located in the posterior-superior aspect of the right external auditory canal. The lesion was excised. Following the histopathologic diagnosis of the middle ear adenoma (neuroendocrine adenoma of the middle ear), a high resolution computed tomography (HRCT) was performed and this showed an extensive osteolytic defect mostly involving the mastoid air cells of the mastoid process with a partial destruction of the middle ear cavity. This defect was filled with a mass-like lesion with the density of soft tissue which bulged to the external auditory canal. The rest of the mastoid air cells were opacificated (Fig. 1). A right posterior tympanotomy and mastoidectomy were performed revealing gray and brown soft tissue in the middle ear cavity and the mastoid, which was submitted for histopathologic examination. Seven months later, a “second-look” tympanomastoidectomy was performed and it showed only nonspecific granulation tissue in the mastoid. The patient is without evidence of recurrence 5 years after the last surgery.

Histopathologic findings

The specimen from the external auditory canal and lesion that was removed from the middle ear exhibited a neoplasm composed of closely packed, sometimes back-to-back glandular structures formed by small uniform cuboidal or cylindrical cells (Fig. 2). Small solid islands were also present and these dominated in the middle ear specimen. Immunohistochemical staining was positive for synaptophysin (polyclonal, 1:400, NeoMarkers, Westinghouse) both in the glandular and solid areas (Fig. 3) and negative for chromogranin A (DAK-A3, 1:300, DAKO, Glostrup). The proliferative index (Ki-67, 1:1000, DAKO, Glostrup) was less than 1 %. In addition, cornified masses and debris compatible with fragments of cholesteatoma were seen in the external auditory canal. The “second-look” tympanomastoidectomy showed only nonspecific granulation tissue in the mastoid.

Discussion

There are several lesions occurring in the middle and inner ear which can extend into the external auditory canal and thus be encountered in dermatopathological practice. These include neuroendocrine adenoma of the middle ear (middle ear adenoma), endolymphatic sac tumor (Heffner’s tumor), and paraganglioma, a tumor which occurs in this location nearly exclusively in women. Occasionally, these neoplasms are mistaken for ceruminous gland tumors: a critical review by Thompson et al. indicated that a significant number of lesions reported as ceruminous neoplasms in fact represented some of these entities (2).

Middle ear adenoma (neuroendocrine adenoma of the middle ear) rarely protrudes into the external ear canal. In a series of 48 neoplasms, only 3 extended in the external auditory canal (3). It is a biologically inert tumor which usually shows no destructive local growth (4). Neuroendocrine differentiation which can be identified immunohistochemically is a constant feature, but several antibodies should be applied due to variations in immunoreactivity from case to case. Focal pagetoid migration into the overlying epithelium has been documented in a few cases, including ones protruding into the external ear canal (3,5).

Middle ear adenoma is closely related to carcinoid tumors of the middle ear (6). In fact, these two tumors merge imperceptibly, in the sense of manifesting various degrees of combined exocrine and neuroendocrine differentiation and therefore can be regarded as analogous to adenocarcinoids or amphicrine neoplasms of other sites (7).

In conclusion, rare patients with neuroendocrine adenoma of the middle ear present with a mass in the external ear canal as the first sign of the disease. Recognition and awareness of this neoplasm is important as these patients need to be clinically investigated to confirm middle-ear disease and require complex surgical treatment.

Address for correspondence:

Denisa Kacerovská, MD

Sikl’s Department of Pathology

Charles University, Medical Faculty Hospital

Alej Svobody 80, 304 60, Pilsen, Czech Republic

tel: +420-377104651, Fax: +420-377104650

e-mail: kacerovska@medima.cz