An Unusual Case of Pancreatic Ductal Adenocarcinoma With Synchronous Rectal Metastasis in a Younger Female.

Background: Pancreatic cancer (PC) remains one of the leading causes of cancer mortality in the United States. There has been a concerning trend in recent years where younger females are experiencing a faster annual percentage increase than their male counterparts (2.36% vs. 0.62%). Metastasis of pancreatic ductal adenocarcinoma (PDAC) to the rectum is uncommon, and synchronous rectal metastasis occurs even less frequently. Case Presentation: We describe a case of a 49-year-old woman with Stage IV PDAC with synchronous rectal metastases. The hallmark of her symptoms was hematochezia and epigastric pain, initially misdiagnosed as gastritis. However, the patient returned with new laboratory and imaging findings of the synchronous pancreatic tail and rectal masses confirmed by histology. Immunohistochemistry was crucial in distinguishing a primary PC from a rectal primary. The patient continues to undergo chemotherapy 14 months after presentation. Conclusion: This represents the first documented case in the United States and the sixth reported case of synchronous rectal metastasis from PDAC. It highlights the increasing incidence and the demographic shift of PC among young women in the United States, which needs further investigation. The case adds to our knowledge of the unusual metastatic pattern of PDAC and the need for a multidisciplinary approach, including the role of immunohistochemistry in distinguishing between the primary etiology of malignancy to establish an accurate diagnosis, instituting an appropriate treatment plan, and preventing unwanted treatment and surgeries.