Nodulocystic Acne
There are many types of acne, but few have actual cysts. Nodulocystic acne, however, is a severe type of acne characterized by cysts that may measure several centimeters in diameter. These cysts may occur singly or be widespread; they occur over the face, neck, scalp, back, chest, and shoulders. They are often painful.
While a true cyst is an abnormal dilation of normal skin structure, an acne cyst is a nodule of inflammation arising from an acne lesion or a cyst that develops in the outer layer of skin. They are often filled with a thick, yellow, pus-like fluid. Drainage should take place in a doctor’s office, not at home in less sterile conditions. Cysts occuring together can cause patches of inflammation and cell destruction leading to acne conglobata and scarring.
Nodulocystic acne should be treated aggressively with antibiotics, isotretinoin, or corticosteroids. Some cysts that don’t respond to treatment may need to be surgically drained and/or excised.
http://www.iscid.org/encyclopedia/Nodulocystic_Acne