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When we think about malignancies that

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affect the external auditory canal,

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we usually have to think about cutaneous spread of

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skin lesions into the external auditory canal.

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Malignancies that are primarily located within the

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external auditory canal are relatively uncommon.

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It's more likely that the sun-exposed

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areas of the external ear

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will be the site of the primary malignancy,

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which secondarily will grow into

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the external auditory canal.

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When you have external auditory canal

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invasion by a cutaneous lesion,

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it's much worse prognosis than if you just have

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it on the pinna of the ear or the contrabo,

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or the tip of the ear, or the top of the ear,

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which is the sun-exposed portion.

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If you have both cartilaginous and bony involvement

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of the external auditory canal,

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again, you have an even worse prognosis.

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So most of these are going to be the

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top three: basal cell carcinoma,

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squamous cell carcinoma, and melanoma,

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all of these generally occurring outside

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on the external ear and growing inward.

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So these are in sun-exposed portions

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of the external ear.

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Squamous cell carcinoma has the

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worst prognosis of these.

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Melanoma may have the possibility

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of hematogenous spread.

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Besides the skin cancers,

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the external auditory canal malignancy, that would be

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also associated in a pediatric patient population

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would be rhabdomyosarcomas.

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Here's a patient that on CT scan,

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you notice has erosion of the skin surface

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and extension to the skull base.

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This patient actually had exposed bone here where

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the skin cancer had eroded down

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to the level of the bone.

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And there is soft tissue thickening along the

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temporalis muscle and the temporal region of the

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scalp overlying the squamosal portion

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of the temporal bone.

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When we looked at the temporal

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bone CT on this patient,

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we noted that there was erosion into the mastoid air

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cells from the skin of the external auditory

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canal's cartilaginous portion.

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There are multiple little bites out of this bone

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from the malignancy growing into

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the mastoid air cells.

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You notice that this patient had soft tissue which

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extended even to the tympanic

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membrane on the right side.

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This is a patient who neglected the skin cancer that

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was growing on the left side of the patient's

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scalp and extended to the ear.

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At this juncture, really,

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we can't even identify where the ear is.

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And you notice that there is gross erosion of

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the temporal bone by this huge malignancy.

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Looking at the bone windows,

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you can identify the temporomandibular joint,

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with this being the mandibular condyle.

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And posterior to the mandibular condyle,

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we would normally expect to see the anterior

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wall of the external auditory canal.

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So let me draw that in for you.

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So normally, you would have the Glenoid fossa

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of the temporal mandibular joint,

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this being the mandibular condyle.

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And then just behind that,

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you would have the external auditory canal with

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both bony as well as cartilaginous portion.

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As you can see on this bone window,

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instead we have this very large soft tissue mass, which has

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eroded even the mastoid air cells and the external

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auditory canal cannot even be distinguished.

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Somewhere in here is the facial nerve.

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Although this patient did present with facial nerve

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palsy as well due to the malignant

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spread to the facial nerve canal.

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I mentioned rhabdomyosarcoma as the most common

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pediatric malignancy that may affect the external

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auditory canal. In that location,

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it can erode into other portions

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of the temporal bone.

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And this is what you're seeing

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here on the left hand image.

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Although you have a small component of the external

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ear portion of this rhabdomyosarcoma,

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what you're seeing is opacification of the mastoid

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air cells and even into the petrous portion of the

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temporal bone as this malignancy has spread

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throughout the temporal bone.

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The temporal bone is one of the parameningeal sites

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rhabdomyosarcoma, which is associated

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with a worse prognosis.

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On the right hand side,

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you see another patient who had a temporal

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bone enhancing malignancy.

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And this was a second decade of life child.

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And the patient presented with a small mass that was

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identified in the external auditory canal, which was

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effectively the tip of the iceberg.

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Because on this example,

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you see that this mass has grown from the mastoid

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air cells throughout the middle ear cavity.

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It's probably eroded through the anterior

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epitympanic space to involve the adjacent

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temporal lobe. And not only that,

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but we are seeing in Meckel's cave region,

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here's the normal Meckel's cave,

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that there is enhancing tissue which extends to

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the posterior margin of the cavernous sinus.

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So going from the expected location of the fifth

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cranial nerve to involve the posterior cavernous sinus region

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where it may affect any number of the cranial

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nerves, including cranial nerve three, four,

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six or five.