Thickened epidermis (Acanthosis)

Thickened Epidermis (Acanthosis)

This usually results from keratinocyte hyperplasia and features acanthosis of the epidermis. Often there is associated hyperkeratosis.

Check it to see if there is any cytological atypia of the keratinocytes to indicate Bowen's disease. If not consider benign lesions such as seborrhoeic keratosis, clear cell acanthoma, poroma, hidradenoma 

If koilocytosis then a wart.

 Otherwise a lot of chronic diseases eg Lichen simplex and Psoriasis will show a thickened epidermis but look out for some Deep fungal infections, TB of the skin and Reactive perforating collagenosis and the much rarer halogenodermas.

Pseudoepitheliomatous Hyperplasia is a term used to describe marked acanthosis that may simulate well differentiated squamous cell carcinoma. The following conditions may show this feature but look for it in Prurigo nodularis and hypertrophic lichen planus. 

Also Halogenodermas, Deep fungal infections, Prurigo nodules, Pemphigus vegetans, Keratoacanthoma, Orf, Condyloma acuminata, Granular cell tumour, Tuberculosis verrucosa cutis, and Acanthoma fissuratum.

Reticulated Acanthosis   Confluent and reticulated papillomatosis, Acanthosis nigricans, Reticulated Seb K and Dowling Degos Disease (Reticulated pigmented dermatosis of the flexures)