Clinical history: 50 year old male lesion on forehead.
What is the diagnosis, the main differential, and pathological features that help to distinguish between them?
At low power this lesion shows a well defined crater with prominent lipping at the edges (compare to the previous case).
Note the absence of atypia in the cells that form the lip.
Another low power clue is the relatively disorganized horn, as compared to the vertically structured horn in the verrucus lesion. There is a brisk inflammatory response, which disrupts the basal layer.
There is disorganized maturation, however in this case the nuclear atypia is mild. This is one of the common lesions that can give rise to prominent hyperkeratosis (cutaneous horn).