This is a conical piece of tissue, the base of which is a disc of skin some 2.5 cm in diameter. The
cone is 3 cm high, the outer surface is black and probably partly necrotic.
This woman developed a painless lump on her forehead some 6 weeks before admission;
initially, this was a small lump like a wart, with a crust on top; it was treated with caustic soda,
which made it black, but did not reduce the size. It became progressively enlarged and bled several
times. It was excised and the histology was that of a keratoacanthoma.