A case of needle tract seeding of pancreatic adenosquamous carcinoma after a single endoscopic ultrasound-guided tissue acquisition.

Needle tract seeding (NTS) is a rare complication of endoscopic ultrasound-guided tissue acquisition (EUS-TA). Herein, we report the case of an 83 year-old man who presented with a solid mass in the pancreatic tail, measuring 35 mm in diameter, with cystic degeneration. EUS-TA was performed using a 22-gauge biopsy needle, with a single puncture via the stomach; however, no definitive pathological diagnosis was achieved. Due to the strong suspicion of malignancy, surgery was performed at the patient's request, and the postoperative pathological diagnosis was pancreatic adenosquamous carcinoma. One year after surgery, computed tomography revealed a string of bead-like nodules within the gastric wall. Esophagogastroduodenoscopy revealed three submucosal, tumor-like raised lesions aligned in a row on the upper posterior wall of the gastric body. EUS detected a solid mass with cystic degeneration. Histological findings from EUS-TA specimens were consistent with those from the pancreatic resection specimen, leading to a diagnosis of NTS. Although reports of NTS have been increasing in recent years, cases of NTS occurring after only a single puncture remain extremely rare. This case clearly demonstrates that NTS can occur even after a single puncture, highlighting the importance of obtaining thorough informed consent regarding this risk prior to performing EUS-TA.