Eccrine porocarcinoma and Bowen's disease arising in a seborrhoeic keratosis.

An association between seborrhoeic keratosis (SK) and malignant tumours is considered to be rare. We observed a case of eccrine porocarcinoma and Bowen's disease (BD) occurring synchronously, forming one lesion in a SK on the abdomen. It is controversial whether malignant neoplasms arising in SK occur only by chance or if pre-existing SK plays a role in pathogenesis. This case suggests an implication of pre-existing SK in the subsequent development of both BD and eccrine porocarcinoma.