Neuroendocrine adenoma middle ear (NAME) is a tumor which arises from a specific anatomic site: middle ear. NAME is a benign glandular neoplasm of middle ear showing histologic and immunohistochemical neuroendocrine and mucin-secreting differentiation (biphasic or dual differentiation).

Classification

Neuroendocrine adenoma of the middle ear has gone by several different names, including middle ear adenoma, carcinoid tumor, amphicrine adenoma, adenocarcinoid, and adenomatoid tumor of middle ear. The various names have created some confusion about this uncommon middle ear tumor. Regardless of the name applied, the ''middle ear'' anatomic site must be known or confirmed.

Signs and symptoms

This uncommon tumor accounts for less than 2% of all ear tumors. While patients present with symptoms related to the middle ear cavity location of the tumor, the tumor may expand into the adjacent structures (

external auditory canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum and is about in length and in diameter. Struct ...

mastoid bone The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles (via tendons) and it has openings for blood vessels. From its borders, ...

, and

eustachian tube In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in d ...

). Patients come to clinical attention with unilateral (one sided)

hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Language ...

, usually associated with decreased auditory acuity, and particularly

conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound waves anywhere along the pathway through the outer ear, tympanic membrane (eardrum), or middle ear ( ossicles). If a conductive hearing loss occurs in conjunction wi ...

if the ossicular bone chain ( middle ear bones) is involved.

Tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...

(ringing),

otitis media Otitis media is a group of inflammatory diseases of the middle ear. One of the two main types is acute otitis media (AOM), an infection of rapid onset that usually presents with ear pain. In young children this may result in pulling at the ear, ...

, pressure or occasionally ear discharge are seen. At the time of otoscopic exam, the

tympanic membrane In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air ...

is usually intact, with a fluid level or mass noted behind the ear drum. Even though this is a "neuroendocrine" type tumor, there is almost never evidence of neuroendocrine function clinically or by laboratory examination.

Imaging findings

In general, an axial and coronal bone computed tomography study without contrast will yield the most information for this tumor. The tumor appears as a soft tissue mass usually within a well-aerated mastoid bone. The features of chronic otitis media are not usually seen. Bone invasion and destruction are usually not seen in this tumor which expands within the mesotympanum (middle ear cavity). Encasement of the ossicles is usually present. There may be an irregular margin at the periphery, especially if the tumor has been present for a long time, with associated bone remodeling.

Pathology findings

At the time of surgery, the tumor tends to peel away from the adjacent bones, although not the ossicles. It is usually fragmented, soft, rubbery and white to gray-tan. Due to the anatomic confines of the region, tumors are usually <1 cm. The tumors arise below the surface, are unencapsulated, and have an infiltrative pattern of growth, composed of many different patterns (glandular, trabecular, cords, festoons, single cells). The tumor shows duct-like structures with inner luminal, flattened cells and outer, basal, cuboidal cells. The cells may have an eccentrically placed nucleus. The nuclear chromatin distribution is " salt-and-pepper", giving a delicate, fine appearance. Nucleoli are small with inconspicuous mitoses. There may be secretions in the gland tumor. It is possible to see a concurrent

cholesteatoma Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process. Cholesteatomas are not cancerous as the name may suggest, but can cause significant problems because of the ...

Histochemistry

It is possible to see intracytoplasmic as well as luminal mucinous material highlighted by a Periodic acid-Schiff (PAS) or

Alcian blue Alcian blue () is any member of a family of polyvalent basic dyes, of which the Alcian blue 8G (also called Ingrain blue 1, and C.I. 74240, formerly called Alcian blue 8GX from the name of a batch of an ICI product) has been historically the mo ...

stain.

Immunohistochemistry

The tumor cells differential stain with markers for epithelial and neuroendocrine immunohistochemistry markers. * Both cell types positive: pancytokeratin, CK7, CAM5.2 * Inner luminal cells positive: CK7 * Outer basal cells positive: chromogranin, synaptophysin, CD56, and human pancreatic polypeptide (HPP).

Electron microscopy

Scanning electron microscopy shows two distinct cell types: * Type A: Apical dark cells with elongated microvilli and secretory mucus granules; * Type B: Basal cells with cytoplasmic, solid, dense-core

neurosecretory Neurosecretion is the storage, synthesis and release of hormones from neurons. These neurohormones, produced by neurosecretory cells, are normally secreted from nerve cells in the brain that then circulate into the blood. These neurohormones are sim ...

granules. In a few areas, transitional forms with features of both cell types may be present.

Diagnosis

From a pathology perspective, several tumors need to be considered in the differential diagnosis, including

paraganglioma A paraganglioma is a rare neuroendocrine neoplasm that may develop at various body sites (including the head, neck, thorax and abdomen). When the same type of tumor is found in the adrenal gland, they are referred to as a pheochromocytoma. They ar ...

ceruminous adenoma A ceruminous adenoma is a benign glandular neoplasm which arises from the ceruminous glands located within the external auditory canal. These glands are found within the outer one third to one half of the external auditory canal, more common alo ...

, metastatic adenocarcinoma, and

meningioma Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing o ...

Management

The tumor must be removed with as complete a surgical excision as possible. In nearly all cases, the ossicular chain must be included if recurrences are to be avoided. Due to the anatomic site of involvement, facial nerve paralysis and/or paresthesias may be seen or develop; this is probably due to mass effect rather than nerve invasion. In a few cases, reconstructive surgery may be required. Since this is a benign tumor, no radiation is required. Patients experience an excellent long term outcome, although recurrences can be seen (up to 15%), especially if the ossicular chain is not removed. Although controversial, metastases are not seen in this tumor. There are reports of disease in the neck lymph nodes, but these patients have also had other diseases or multiple surgeries, such that it may represent iatrogenic disease.

Epidemiology

Most individuals come to clinical attention during the 5th decade, although the age range is broad (20 to 80 years). There is an equal gender distribution.