Epithelial cystApr 1, 2002 . Occasionally, a dark keratin plug (a comedo) can be seen overlying the cyst cavity. .This is a report of a case of epithelial cyst of the spleen in an 8-year-old boy. The cyst showed s. It is believed that the first stage in pathogenesis of a corneal epithelial cyst is the displacemen. Many people often call any small, painless lump under the skin "sebaceous cysts. " But tho.