Pilar cyst and epidermoid cyst are red painful blisters found on the scalp. It is also called as sebaceous cyst since it contains sebum (an enzyme secreted by sebaceous gland). The cysts are filled with contents similar to cottage cheese looking very much like toothpaste. More than 90% of pilar cyst occurs on the scalp. It is known by the name of trichilemmal cyst which is harmless and benign.
The pilar cyst is closed sac like structure developing on the scalp. If it develops on the subcutaneous layer of the scalp it is called intradermal cyst (only on 5-10%) and very often it occurs on the cutaneous layer. These cysts can be sporadic and are inherited from parents.
In rare cases the pilar cyst contains single or group of proliferating cells that can turn into tumors (2%). This type of cyst grows in size and extends up to 25cm in diameter that causes ulcer like growth. Though they are harmless still it can be aggressive and recur again after it heals. Basically pilar cyst contains a lining and the contents. The lining looks very much like the outermost layer (epidermis) of the skin and looks like roots of hairs. The contents of the cyst include cheese like material made of keratin. Pilar cyst is more common in women than men. It develops on middle aged and old aged people.
Pilar Cyst Symptoms :
Pilar cysts are mostly skin colored and are round/oval shaped bumps lying under the skin. Most of them occur as single nodule and sometimes it occur as group of lesions. There will not be any punctum on the cyst. It looks like inflamed growth of the skin red in color. The lining of the cyst will fuse with the epidermal layer to form a crypt which will discharge and ooze out contents until it finally resolves. Pilar cysts are red colored sores emitting foul smelling pus. It looks embarrassing for the person. Sometimes it contain dark plug in the center though which it discharges the contents inside.