This tumor is composed of the epithelial components of the most proximal (trichogenic) portion of the hair follicle associated with an imperfect hair cortex type of keratinization (ghost cells or shadow cells). Though not often mentioned, other forms of keratinization may be present. The most primitive cellular component consists of basophilic cells having scanty cytoplasm and nuclei that occasionally overlap to some extent. Mitotic activity can be prominent within this cell population. In addition, cells that are more squamoid as well as cells having transitional features may also be present. Calcification is common as is a granulomatous reaction to various keratinous products. Eosinophilic trichohyalin granules , basophilic keratohyalin granules and /or ossification are found in minority of cases.

	Very low power view (direct scan of glass slide). Multiple types of keratinization plus a mixture of epithelial elements produce a swirled or geographic appearance at this power.
	A high power view. Ghost cells (shadow cells) are associated with a granulomatous reaction. The ghost cells have a yellowish cast and this is common in this type of keratin.
	A medium power view. Basaloid cells that have nuclei that sometimes overlap slightly produce shadow cells after going through eosinophilic transformation of the cytoplasm.
	Another high power view. Basophilic cells are in the left side of the picture. Transitional cells are in the right side of the picture, and these are undergoing eosinophilic cytoplasmic alteration similar to that found in the basophilic cells in the previous picture.
	Another high power view. Going from right to left, there is a progression of basophilic cells, transitional cells, and squamous cells, which have a stratum granulosum. The keratin produced by the squamous cells is more amorphous than the shadow cell type of keratin.

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