Sarcoma of the lung in a pacemaker pocket--simple coincidence or oncotaxis?

An 82-year-old man developed a soft-tissue sarcoma in the subpectoral pocket of a titanium-covered pulse generator that had been replaced 8 months previously without evidence of tumor. The tumor represented a metastatic manifestation of a malignant fibrous histiocytoma situated in the contralateral lower pulmonary lobe. The patient died some weeks postoperatively due to cachexia. Autopsy revealed no further metastases. The appearance of cancer in patients with pacemakers is probably coincidental and not related to material or electrochemical stimulation, although the site of the generator pocket might be oncotactic because of the irritation that would trap tumor cells and provide disruption in the intracellular endothelial barrier allowing migration of the tumor cells into tissues. Possible causes and relationships are reviewed.