Intranuclear particles in keratoacanthoma: possible association with malignant degeneration

Electron microscopic investigation of 12 patients with keratoacanthoma is reported. Intranuclear virus-like particles, as described by Zelickson and Lynch, were seen in 3 cases; 2 of these subsequently underwent malignant degeneration. These findings suggest that it is particularly important to exclude the possibility of malignant change in those tumours when intranuclear particles are found.