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?
irritated seborrheic keratosis
Overall the lesion is acanthotic, composed of monotonous epithelial cells, however there are areas with more intensely eosinophilic cytoplasm which may raise the possibility of dysplasia.
These areas represent the formation of early 'squamous eddies', and the continued nuclear monotony combined with the remainder of specimen which shows only seborrheic keratosis establish the diagnosis.
This is one of the common lesions that can give rise to prominent hyperkeratosis (cutaneous horn).