Medulla, cortex, cuticle, internal root sheath external root sheath

1. Sebaceous 2. Eccrine 3. Apocrine

Sheath of the hair follicle below the sebaceous gland and the dermal papilli

Holocrine

reactive epidermal hyperplasia forming irregular acanthosis - mimics cancer

Thermoregulation - Under nerve control - direct arteriovenous diversion of blood - found in the dermis in the fingertips and toes and ears

epidermoid cyst Lamellated loose keratin Lined by stratified squamous epithelium with a granular cell layer

tricholemmal cyst/ pilar cyst found on the scalp keratin compact No granular cell layer in the epidermis

Pyogenic granuloma AKA lobular capillary haemangioma lobular proliferation of capillaries epidermal ulceration common collarette from elongated rete ridges pale oedematous stroma (granulation like)

Lies in the dermis, ill defined margins, irregularly arranged spindle cells Pseudoepitheliomatous hyperplasia

collagen 1A1 promter juxtaposed with platelet derived growth factor B leading to over expression of PDGFb (receptor Tyrosine kinase)

Basket weave hyperkeratosis Pseudohorn cysts

Fibroblast growth factor receptor 3 (tyrosine kinase)

Numerous Seb K - paraneoplastic secondary to tumour cells producing TGFalpha (GI tract cancers)

Seb K variant typically involves follicular infundibulum Squamous eddies +/- horn cysts and orthokeratosis Lobular non-infiltrative growth pattern