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Abdominal Pain and an Appendiceal Mass

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A 68-year-old woman with a history of uterine carcinoma (unknown histology) diagnosed and treated 30 years prior with hysterectomy and adjuvant chemotherapy in another country presented with 2 months of generalized abdominal pain and distention. She had no fevers, nausea, vomiting, diarrhea, constipation, blood in the stool, or weight loss. She was not taking any medications. On examination, her temperature was 36.9 °C; heart rate, 72/min; blood pressure, 132/68 mm Hg; and body mass index, 25 (calculated as weight in kilograms divided by height in meters squared). Results of complete blood cell count and serum chemistries were unremarkable, with no leukocytosis and normal differential count. Abdominal examination demonstrated mild distention without fluid wave and mild right lower abdomen and suprapubic tenderness. Computed tomography (Figure 1) and magnetic resonance imaging demonstrated pelvic ascites and an enhancing lesion at the base of the cecum. Two attempts at ultrasound-guided paracentesis were nondiagnostic because of acellular specimens. Serum CA-125 level was normal; carcinoembryonic antigen (CEA) level was 18 ng/mL (reference, <5 ng/mL).

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Appendiceal mucinous neoplasm (AMN)

A. Perform laparoscopic appendectomy and peritoneal biopsy

The key to the likely diagnosis in this case is the presence of an appendiceal mass with a subacute presentation of symptoms. Of the choices listed, appendectomy with peritoneal biopsy is the most appropriate next step, as it will provide a definitive diagnosis. Repeat aspiration with cytology (choice B) is unlikely to yield the diagnosis, as the fluid is typically hypocellular and too viscous to aspirate. Colonoscopy (choice C) may demonstrate an extrinsic bulge at the appendiceal orifice, but biopsies of the appendiceal mucosa are not generally feasible via colonoscopy. Treatment with antibiotics (choice D) is inappropriate given the subacute presentation, lack of infectious symptoms, and imaging concern for neoplasia.

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Article Information

Corresponding Author: Jonathan C. King, MD, Department of General Surgery, University of California, Los Angeles, 1304 15th St, Ste 102, Santa Monica, CA 90404 (Joking@mednet.ucla.edu).

Published Online: July 17, 2020. doi:10.1001/jama.2020.4707

Conflict of Interest Disclosures: None reported.

Additional Contributions: We thank the patient for providing permission to share her information.

References
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Fournier  K , Rafeeq  S , Taggart  M ,  et al.  Low-grade appendiceal mucinous neoplasm of uncertain malignant potential (LAMN-UMP): prognostic factors and implications for treatment and follow-up.   Ann Surg Oncol. 2017;24(1):187-193. doi:10.1245/s10434-016-5588-2PubMedGoogle ScholarCrossref
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