Critical ReviewCornoid Lamellation Revisited Apropos of Porokeratosis With Emphasis on Unusual Clinicopathological VariantsBiswas, Asok MD, FRCPath, DipRCPathAuthor Information Department of Pathology, Alexander Donald Building, Western General Hospital, Edinburgh, United Kingdom. Reprints: Asok Biswas, MD, FRCPath, DipRCPath, Department of Pathology, Alexander Donald Building, Western General Hospital, Edinburgh, EH4 2XU, United Kingdom (e-mail: [email protected]). The author declares no conflicts of interest. The American Journal of Dermatopathology: February 2015 - Volume 37 - Issue 2 - p 145-155 doi: 10.1097/DAD.0000000000000039 Buy Metrics Abstract Porokeratosis is a family of several disorders characterized histologically by the presence of cornoid lamellae. The presence of cornoid lamellae represents an abnormal form of keratinization, which unifies all types of porokeratosis. A significant variation in lesional morphology can result from peculiarities involving the cornoid lamellae and changes related to epidermal hyperplasia and dermal inflammation. This diversity has led to the recognition of several unusual clinicopathological variants of porokeratosis in recent years. Cornoid lamellation, however, is not pathognomonic of porokeratosis and can be seen in some inflammatory and inherited cutaneous disorders and also as an incidental finding. Some of these conditions can be confused with an atypical presentation of porokeratosis and vice versa. An awareness of the broad morphological spectrum of porokeratosis is crucial to avoid missing the diagnosis when appearances are far from typical. This issue is critical in patient management given the potential premalignant nature of porokeratosis. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.