What happened, in summary

A 40-year-old woman was undergoing surveillance after surgery for right breast cancer when PET imaging found an unexpected FDG-avid tumor in the middle thoracic esophagus. Her breast cancer had been resected 5 years earlier and had not recurred. She had no major symptoms or notable clinical findings when the esophageal lesion was discovered. CT showed a low-absorption area, MRI showed a signal similar to muscle tissue, and endoscopy found a submucosal tumor about 25 cm from the incisors. Endoscopic ultrasound showed an approximately 20 mm low-echoic solid mass arising from deeper layers of the esophageal wall. Fine-needle aspiration found spindle tumor cells. Immunohistochemistry was positive for desmin and negative for CD34 and c-kit, supporting leiomyoma, a benign smooth-muscle tumor. Because the lesion showed FDG uptake and the biopsy sampled only part of it, leiomyosarcoma could not be fully excluded before complete removal. She underwent peroral endoscopic tumor resection, or POET, using a 3.5 mm Clutch Cutter under general anesthesia. The tumor was removed en bloc without severe intraoperative complications. A chest radiograph immediately afterward showed mediastinal emphysema, which was managed conservatively with antibiotics. Her diet restarted on postoperative day 6, and she was discharged 11 days after the procedure. Final pathology confirmed a 19 × 15 mm leiomyoma, with desmin and αSMA positivity and S100, CD117, and GLUT1 negativity. The case reflects successful minimally invasive removal of a benign esophageal tumor found during breast cancer surveillance. This outcome also supported that the PET-avid lesion was not breast cancer recurrence or esophageal cancer, but a benign tumor safely managed with an organ-preserving endoscopic approach.