Cluster of Vacuolated Spinous Keratinocytes: A Clue to Cornoid Lamellation and a Case of Porokeratosis Disseminata.

Cornoid lamella is a definitive diagnostic feature of porokeratosis, a disorder of keratinization that has various different clinical presentations. A tiered column of parakeratosis and a diminished granular layer with dyskeratotic keratinocytes at the column base are all useful and known features of cornoid lamellation. We have found a cluster of vacuolated spinous cells to be a reliable fourth feature of cornoid lamellation and a feature when present alone to be a reliable sign of impending cornoid lamellation on deeper sections. Furthermore, we present a novel clinical phenotype of disseminated papular porokeratosis with effective clinical response to combination of phototherapy, oral and topical retinoids, and topical vitamin D derivative, which too contained all 4 features of cornoid lamellation.