Histopathology of a<unk> , from internal (top) to external (bottom):- Solid eosinophilic-staining keratin.- Swollen pale keratinocytes, which increase in height closer to the interior.- Small, cuboidal, dark-staining basal epithelial cells in a palisade arrangement, with no distinct intercellular bridging.- Fibrous capsule.There is no granular cell layer (in contrast to an epidermoid cyst).<unk> s are derived from the outer root sheath of the hair follicle. Their origin is currently unknown, but they may be produced by budding from the external root sheath as a genetically determined structural aberration. They arise preferentially in areas of high hair follicle concentrations, so 90% of cases occur on the scalp. They are solitary in 30% and multiple in 70% of cases. Histologically, they are lined by stratified squamous epithelium that lacks a granular cell layer and are filled with compact "wet" keratin. Areas consistent with proliferation can be found in some cysts. In rare cases, this leads to formation of a tumor, known as a proliferating<unk> . The tumor is clinically benign, although it may display nuclear atypia, dyskeratotic cells, and mitotic figures. These features can be misleading, and a diagnosis of squamous cell carcinoma may be mistakenly rendered.
Trichilemmal cyst
Trichodiscoma
Trichilemmoma
Proliferating trichilemmal cyst
Trichilemmal carcinoma
Nabothian cyst
Trichofolliculoma
Hidradenoma