An unusual hybrid cyst in Gardner's syndrome with partial differentiation toward the inner root sheath

A 26-year-old man with Gardner's syndrome had numerous subcutaneous nodules over almost his entire body. Histologically, one of them revealed an unusual so-called hybrid cyst composed of epidermal type keratinization and inner root sheath type keratinization. The histologic findings and the possibility of cutaneous cysts based on hair matrix differentiation, more specifically partial differentiation toward the inner root sheath, are discussed.