Low-grade appendiceal mucinous neoplasm: A case report

Rationale: Low-grade appendiceal mucinous neoplasm (LAMN) is a clinically rare tumor that predominantly occurs in females and presents with nonspecific symptoms, often resulting in misdiagnosis. While postoperative pathology remains the gold standard for diagnosis, accurate preoperative identification through various diagnostic methods is essential for effective treatment planning. To raise awareness of this condition, we present a case of a middle-aged male diagnosed with LAMN.

Patient concerns: A 52-year-old male presented to outpatient clinic with right lower abdominal pain lasting 1 day. He described the pain as continuous cramping, exacerbated by movement and coughing, with associated nausea.

Diagnosis: Physical examination revealed tenderness in the right lower quadrant and a palpable mass measuring approximately 6.5 cm × 5.0 cm, with poor definition and limited mobility. An elevated white blood cell count (16.2 × 109/L) and a mixed cystic and solid mass were noted, prompting admission for further evaluation. Further, abdominal enhanced computed tomography revealed a mixed-density lesion in the right ileocecal region, measuring approximately 6.5 cm × 5.0 cm. This finding was suggestive of an appendiceal mucinous neoplasm, with mucinous adenocarcinoma remaining a possibility that could not be excluded.

Interventions: The patient underwent a laparoscopic right hemicolectomy on June 5, 2024, and the gross specimen showed: a 6.5 cm × 5.0 cm mass was found in the appendix area on the surface of the intestinal tube, a large amount of jelly was found after incision, and the mass was connected to the intestinal cavity.

Outcomes: The patient recovered well after surgery, the abdominal drainage tube was pulled out on the 8th day after surgery, and the patient was discharged on the 13th day after surgery. Postoperative examination showed LAMN and mucus accumulation in the wall of the appendix with a foreign body giant cell reaction, acute attack of chronic appendicitis, and suppurative inflammation with peripheral inflammation. Postoperative diagnosis: LAMN; acute chronic appendicitis attack.

Lessons: As a rare clinical gastrointestinal tumor, LAMN lacks specific clinical manifestations, and its diagnosis depends on postoperative examination; however, the indications for surgery are clear and the clinical prognosis is good. The key to surgery is to protect the tumor body to avoid rupture and cause the development of peritoneal pseudomyxoma (PMP).