Case report and literature review on IgG4-related disease misdiagnosed as pancreatic cancer in a 70-year-old maleA 70-year-old man avoided unnecessary surgery after doctors found a treatable autoimmune condition

BackgroundWhen IgG4-related sclerosing disease (IgG4-RD) involves the pancreas, it frequently manifests as focal mass formation. These lesions clinically and radiographically closely mimic pancreatic ductal adenocarcinoma, often leading to unnecessary invasive interventions. Clarifying the diagnostic difficulties in differentiating focal mass-forming IgG4-RD from malignancies is of great significance for optimizing initial clinical assessment and management workflows.MethodsThis study reports the complete clinical course of a 70-year-old male patient who presented with a complaint of upper abdominal bloating, manifesting as a pancreatic head mass accompanied by a significant elevation of the tumor marker CA19-9 and biliary obstruction. Due to a high preoperative suspicion of malignancy and diagnostic challenges, the patient underwent a pancreaticoduodenectomy. Concurrently, this study conducted a systematic review and analysis of previous literature related to IgG4-RD presenting as focal pancreatic space-occupying lesions to explore the common diagnostic pathways and potential pitfalls in such cases.ResultsThe patient’s postoperative pathological and immunohistochemical examinations ultimately confirmed that the lesion was autoimmune pancreatitis secondary to IgG4-related sclerosing disease, with no malignant components identified. The literature review further indicated that, in the early stages of the disease when clear evidence of systemic involvement is lacking, the space-occupying effect on imaging often dominates the diagnostic pathway, obscuring its immune-mediated inflammatory nature.ConclusionFor patients with suspected pancreatic tumors, incorporating IgG4-RD into the routine differential diagnosis can serve as a beneficial relative reference clue. Provided that malignancy is strictly evaluated and excluded through methods such as endoscopic ultrasound-guided tissue biopsy, early recognition of the disease’s inflammatory characteristics combined with multidisciplinary assessment can facilitate the transition of treatment strategies from surgical resection to pharmacological management, thereby optimizing clinical decision-making and avoiding overtreatment.