P3264 - A Challenging Diagnosis of Low-grade Appendiceal Mucinous Neoplasm Mimicking Ovarian Cancer and Primary Biliary Cholangitis

Tooba Laeeq, MD¹, Kyaw Min Tun, DO², Adam Khattak, DO³, Ali Kia, MD^3
1University of Nevada, Las Vegas, NV; ²Creighton University School of Medicine, Las Vegas, NV; ³Kirk Kerkorian School of Medicine at the University of Nevada, Las Vegas, NV

Introduction: Low-grade appendiceal mucinous tumors (LAMNs) are a rare type of appendiceal tumor, often incidentally found without infiltrative growth. We present a case of LAMN presenting with acute kidney injury, elevated liver markers, and ascites.

Case Description/Methods: A 72 year-old female with no known history presented with worsening abdominal distension for two weeks. Physical exam confirmed a distended abdomen. Labs showed WBC 12.8 k/mm3, lactic acid 2.4 mmol/l, creatinine 5.43 mg/dl (baseline 0.7 mg/dl), AST 120 iu/l, ALT 58 u/l, alkaline phosphatase 468 u/l, and total bilirubin 6.7 mg/dl. Imaging revealed moderate ascites with nodular liver. Paracentesis labs, anti-mitochondrial antibody, anti-smooth muscle antibody, and a liver biopsy were inconclusive. Further workup with a renal biopsy and autoimmune panel were unremarkable. However, CA-125 and CA 19-9 levels were elevated at 1279 u/ml and 95 u/ml, respectively, raising concern for ovarian malignancy. The abnormally thickened endometrial lining was noted on transvaginal ultrasound. A hysterectomy with bilateral oophorectomy and appendectomy was subsequently performed. Histology from the appendix revealed an intact appendix wall with mucinous proliferation suggestive of low-grade appendiceal mucinous neoplasm. Due to the patient’s stability, she was discharged and received outpatient care with gastroenterology for colonoscopy and oncology.

Discussion: LAMNs remain poorly understood and are found in only 0.2-0.3% of the appendectomy specimens. Diagnosis is often incidental and made histopathologically. Treatment of LAMNs varies from a radical appendectomy in patients with in-situ disease to ileocecal resection with hyperthermic intraperitoneal chemotherapy or cytoreductive therapy for pseudomyxoma peritonei (PMP). Unfortunately, PMP has a recurrence rate of 3%. Some data suggests that in the absence of PMP, a CT scan of the abdomen is recommended every six months postoperatively, followed by yearly for four years and biennially for six more years, along with tumor markers (CEA, CA19-9, and CA125). Additionally, colorectal cancer should be excluded with a colonoscopy in these patients due to the associated risks.



Disclosures:


Tooba Laeeq, MD¹, Kyaw Min Tun, DO², Adam Khattak, DO³, Ali Kia, MD³. P3264 - A Challenging Diagnosis of Low-grade Appendiceal Mucinous Neoplasm Mimicking Ovarian Cancer and Primary Biliary Cholangitis, ACG 2024 Annual Scientific Meeting Abstracts. Philadelphia, PA: American College of Gastroenterology.