Case Presentation: A 55-year-old woman presented with abdominal pain and intractable nausea without constitutional symptoms. Abdominal CT showed duodenal obstruction and hydronephrosis. She underwent two EGD/EUS with benign duodenal and celiac lymph node biopsies. Small bowel follow-through revealed near complete obstruction at the level of the duodenum. Abdominal MRI demonstrated a soft tissue mass-like density in the second part of the duodenum abutting the uncinate process of the pancreas as well as retroperitoneal inflammatory changes. HIDA scan was negative. She required bilateral ureteral stents due to hydroureteronephrosis with an acute kidney injury. Dexamethasone was initiated for concern of autoimmune process. Despite this, she had no symptomatic improvement and required TPN. At our tertiary center, EGD/EUS was repeated demonstrating benign duodenal biopsies and showed mucosal changes without evidence of obstruction or pancreatic abnormality. A MRI with contrast showed mild fullness of the pancreatic uncinate process with surrounding stranding and duodenal wall thickening but no defined mass. Lipase was mildly elevated. Pancreatic biopsy was benign with no features of mass-forming lesion. Autoimmune laboratory work up was negative, including a low IgG-4 titer. Serum biomarkers including CEA, CA 19-9 and AFP were normal. After multidisciplinary discussions with advanced endoscopy, surgical oncology, rheumatology and hospital medicine, a diagnostic laparoscopy was deferred due to malnutrition and debility, and the patient underwent gastrojejunostomy and jejunostomy tube placement with biopsies taken during procedure from the right upper quadrant peritoneum. This demonstrated infiltrative epithelioid tumor cells within the fibroadipose tissue that was positive for CK7, CK5/6, GATA3, and p40, and negative for PAX8, CDX2, CK20, TTF1, Ber-EP4, WT1, and calretinin, representing undifferentiated adenocarcinoma of breast origin. After diagnosis, the patient and her family opted for transition to comfort measures.
Discussion: Diagnosis in this case was challenging for multiple reasons including the rarity of metastatic breast cancer in the GI tract. The incidence is only about 1% and usually occurs many years after diagnosis with a median interval time of 7 years. Next, GI metastasis often mimics other GI disorders with our patient having duodenal obstruction with findings of gallbladder sludge, possible pancreatitis and elevated bilirubin. Multiple biopsies were inconclusive, and nonspecific imaging led to consideration of autoimmune processes like IgG-4 related diseases since this patient also had retroperitoneum involvement which is also an extremely rare initial presentation for breast cancer. It is possible that in our patient retroperitoneum metastasis caused direct compression of ureters or by inducing desmoplastic reaction leading to retroperitoneal fibrosis. Diagnosis required immunohistostaining of peritoneal tissue that was obtained surgically. Prognosis for breast cancer with GI and peritoneum spread is poor and surgical treatment is not usually indicated.
Conclusions: This case illustrates the importance of iterative reasoning and testing in cases of diagnostic uncertainty. Involvement of multidisciplinary teams is important for diagnosis, as well as having adequate tissue samples.
