Case 1: Cystic cavity with keratinaceous debris, lined by stratified squamous epithelium and bulbous lobules of keratinocytes extending into the dermis.

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Pilar sheath acanthoma, dilated pore (of Winer), and trichofolliculoma all share similar features of a dilated pore or cystic cavity filled with keratinous debris, very similar to epidermoid inclusion cysts. In the case of a dilated pore of Winer, the lining of the pore is of squamous epithelium with multiple epithelial "buds" that do not form hair shafts. If this lining is forms massive bulbous epithelial buds, then, the entity is called a pilar sheath acanthoma. For trichofolliculoma, there is a central cystic cavity lined by squamous epithelium, however, small secondary hair follicles emanate from this cystic cavity (Busam).

We shall now focus our discussion on pilar sheath acanthoma. Histologically, pilar sheath acanthomas are characterized by a cystic cavity lined by stratified squamous epithelium. The cavity usually contain keratinous debris and opens onto the surface. The cavity wall is lined by numerous lobules of pink keratinocytes, often referred to as tumor lobules, which often extend into the dermis and subcutis. Tumor lobules are composed of outer root sheath epithelium.

Typically affect middle-aged and elderly individuals. They commonly present as small (5-10mm), solitary, skin-colored papule located on the head and neck resembling a comedo. The upper lip is the classic location for these lesions. A central sinus containing a keratin plug is often present.

• Adnexal : Trichofolliculoma