Yes

Yes they can, I have gone to my family doctor and have been diagnosed with an epidermoid cyst in the lower part of my belly button. At first it was a purplish-blue color and recently it got infected and flared up into something that looked like a boil. An epidermoid cyst is basically a cyst formed in a pore in between your skin. Hence epidermoid comes from epidermal. They aren't common but are very possible.

epidermoid

Carcinoma such as squamous cell carcinoma

the four most common types of cysts are: the Arachnoid Cyst, also called the leptomeningeal cyst the Colloid Cyst the Dermoid Cyst and the Epidermoid cyst, also called the Epidermoid tumor try researching those individualy for further detail. :]