Development of a tennis ball-sized tumor at the site of an implanted pacemaker.

A 77-year-old woman who had undergone a pacemaker implantation 6 years previously developed a tumor on the left side of the chest. The mass gradually grew to the size of a tennis ball and was excised along with the pacemaker generator. Histopathological examination revealed that the mass was a chronic expanding hematoma. Although carcinogenesis occurring around a pacemaker has been reported previously, the development of a hematoma has not been reported. Thus, we suggest that when a patient has a mass in the proximity of a pacemaker, chronic expanding hematoma should be considered as one of the differential diagnoses.