Pilmatricoma (pilomatrixoma)
Is a rare benign tumor that grows withing the subcutaneous soft tissues.
it is associated with hair follicle matrix.
The lesion typically presents as a painless, firm, slow growing mass most commonly seen in the head
and neck, but they can also be seen in the trunk and extremities.
Usually seen in children the peak ages are 5-15 years. They can also be seen in adults and
there is a second peak of incidence in adulthood, years 50-65 years.
Recommended treatment is surgical excision.
Sonographically you’ll typically see a hypoechoic to mixed echogenicity ovoid structure within the subcutaneous layer. It does not extend deep to the fascia. It can have echogenic calcifications within
the lesion, there is also usually good posterior acoustic enhancement.
Color doppler usually shows intralesional flow, whereas a dermoid cyst or other
similar lesion will not have internal flow.
Reference:http://emedicine.medscape.com/article/1058965-overview
http://www.jultrasoundmed.org/content/24/10/1397.full
Images credited to:
American Institute of Ultrasound in Medicine (AIUM) Journal
http://www.skin-ultrasound.com/
http://radiologyassistant.nl/
Applied Radiology
http://www.dermis.net/
Sonographic Tendencies 