65 year old male presented to OPD with a large swelling over nape of neck since 10 to 12 years
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Dermoid cysts have been classified as true dermoid cysts, epidermoid cysts and teratoid cysts.
they may result from entrapment of ectodermal tissue of the first and second brachial arches during fetal development or may occur due to traumatic implantation of epithelial cells into deeper tissues.
Dermoid may occur anywhere in the body, with 7% presenting as head-and-neck lesions, most commonly lateral to the eyebrow with lateral eyebrow being the most common location and floor of the mouth, the second most common location .
The essential difference between a dermoid cyst and an epidermoid cyst lies in the presence of skin appendages (eg, sebaceous glands, hair follicles) within the wall of the dermoid cyst and the absence of these features in the epidermoid cyst.
Complex dermoid cysts contain mesodermal elements like cartilage, bone, and fat.
On ultrasound: well defined anechoic masses with posterior enhancement ; may show homogenous internal echoes or heterogenous appearance due to presence of fat, osseous or dental elements.
On CT scans, the central cavity is usually filled with a homogeneous, hypoattenuating (0–18 HU) fluid material. It may appear to be filled with “marbles,” due to the coalescence of fat into small nodules within the fluid matrix . This “sack-of-marbles” appearance is virtually pathognomonic for a dermoid cyst in this location .
Alternatively, the cyst may be heterogeneous on CT scans because of the various germinal components. Fluid-fluid levels with supernatant lipid are possible. The rim of these cysts often enhances following administration of contrast material.
Magnetic resonance imaging (MRI) shows fluid signal due to high protein content, and the areas of fat component will show low signal on fat suppressed images.
Dermoid cysts are T1 hyper- to iso-intense, depending on sebaceous lipid content, and are generally T2 hyperintense.
MRI facilitates visualization of the exact location and extent of cystic lesions in the floor of the mouth and is useful for determining their relationship to the surrounding muscles.
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