Keratoacanthoma

A symmetric crater in the skin filled with keratin (really low power, slide held over condenser)

With peripheral 'lipping' of keratinocytes

Usually in elderly, face-head-neck region, the crater is visible on gross. It is the smooth roundish outline of the lesion that distinguishes it from a squamous carcinoma (plus that there's no dysplasia in spite of cell enlargement towards the center)