Keratoacanthoma has many similarities with SCC (Squamous Cell Carcinoma) and is often very difficult to tell apart, both clinically and pathologically.
KA generally occurs on sun-exposed sights such as the outside of the ears, parts of the face, the back of hands and forearms, and the lower limb.
The lesion is usually pink, light brown or skin coloured. It grows away from the skin in the shape of a dome. KA usually grows to between 1 and 3cm in size, by which time it has a central crusted plug, giving it the classical description of a volcano. Even without a crust, you will feel the scale on a KA.
It’s almost impossible to be clinically certain that a KA is not an SCC – the appearances are very similar even with a dermatoscope.