An unexpected cause of a swollen pacemaker pocket: a case report.

Background: A complication originating from the pacemaker pocket after device implantation can most often be explained by a post-operative pocket haematoma, or, less frequently, by a pocket infection. Both conditions need immediate assessment, dedicated treatment, and specialized follow-up. In rare cases, however, a swollen pacemaker pocket has an alternative diagnosis, which is exemplified by the following case. Case summary: A 70-year-old male patient had a-specific symptoms of fatigue, dyspnoea, and coughing for some weeks. He also noted an evident, new swelling of his pacemaker pocket several months after pacemaker implantation, a procedure that was performed in a high-volume center and without any complication. Ultrasound imaging of the pocket suggested the presence of a soft tissue mass with increased vascularity, rather than a fluid collection or a late organized haematoma. Ultrasound-guided biopsy of the mass was obtained for histopathology analysis and revealed a well-differentiated invasive squamous cell carcinoma. Additional PET-CT imaging demonstrated multiple fluorodeoxyglucose-avid hotspots: a voluminous lesion in the left lung hilum, smaller lesions in the liver, some mediastinal lymph nodes, several bone lesions, and a large mass surrounding the pacemaker. The multidisciplinary oncologic specialty team concluded that the patient had an aggressive metastatic lung carcinoma. The patient refused to undergo further treatment and died 1.5 months after diagnosis. Discussion: To the best of our knowledge, we did not find any earlier reports of a squamous cell carcinoma of the lung spreading to a pacemaker pocket. Presentation of a primary tumour or a metastasis in a pacemaker pocket is extremely rare. Ultrasound imaging with ultrasound-guided biopsy is a fast and reliable method to sample the tissue and to obtain a reliable diagnosis.