[Histologic aspects of seborrheic keratosis]

The histopathological aspects of seborrheic keratosis have been studied in order to establish a basis to their classification upon structural morphology and cytology. The 210 seborrheic keratosis studied could be classified in several patterns among which we must point out the three most important ones: hyperkeratotic, adenoid and acanthotic. This last one can offer two very different images: uniform acanthotic (this one including at the same time, a variant of "small basal cells") and reticular acanthotic. Special mention has to be made as well to the activated and pure forms which, though being the result of evolutive accidental phenomena, no doubt they have very particular and distinctive histopathological aspects. Further, other variants are discussed such a clonal and acantholytic seborrheic keratosis, as well as the significance of inverted follicular keratosis and of melanoacanthoma.