Presentation
Swelling without pain on posterior aspect of external ear for 1-2 years. History of local pain with increased size of swelling for 4-6 weeks.Further history of single episode of discharge from external ear anteriorly weeks ago. No pain, discharge during the last 4 weeks.
Patient Data
There is a thin walled ovoid lesion in region of interest (posterior aspect of external ear). It is compressible. There are low level internal echoes without vascularity. There is focal loss of lesion wall near skin (posteriorly) with protrusion of its content in surrounding soft tissue. There is peri-lesional vascularity.
On deeper (or towards anteriorly) side, there is a hypoechoic tract from lesion reaching up to the ear cartilage. Tract is upto 8-10 mm length. Proximal part of tract shows some echoes with air foci. Deeper most tract is empty. Adjacent ear cartilage shows mild thickening. However, there is no obvious cartilage breach.
Case Discussion
Clinically the patient had an epidermal inclusion cyst on the posterior aspect of the external ear. There was a recent episode of inflammation (with leak) about 4-6 weeks ago and ear discharge (4 weeks back).
Ultrasound shows avascular thin walled lesion with a tract extending to ear cartilage.
Surgical exploration was done. Methylene blue was injected into lesion to see tract extension. However, cartilage perforation could not be seen at the time of surgery.
Histopathology revealed an epidermal inclusion cyst.
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