Appendiceal Neuroendocrine Tumor Masquerading as Acute Appendicitis in a Young Male: A Case Report and Clinical Discussion.

BACKGROUND

Appendiceal neuroendocrine neoplasms (ANENs) are rare tumors of the appendix, most of which are low-grade malignancies. They are often discovered incidentally during surgery for acute appendicitis. This report presents a case of a 29-year-old male with typical manifestations of acute appendicitis. Preoperative imaging and laboratory tests were consistent with acute appendicitis with abscess formation, but postoperative pathology revealed an unexpected appendiceal neuroendocrine tumor. The aim of this report is to improve clinicians' understanding, diagnostic accuracy, and therapeutic decision-making for this condition.

CASE PRESENTATION: A 29-year-old male patient presented with a one-day history of migratory right lower quadrant abdominal pain. Physical examination revealed tenderness and rebound tenderness at McBurney's point, and a positive Rovsing's sign. Laboratory tests showed elevated inflammatory markers (procalcitonin, interleukin-6, ferritin), consistent with acute appendicitis. Ultrasound and CT imaging revealed a thickened appendix with periappendiceal exudation, consistent with acute appendicitis with abscess formation. Emergency laparoscopic appendectomy was performed. Postoperative pathology confirmed an appendiceal neuroendocrine tumor (G1) with serosal and perineural invasion, without lymphovascular invasion, and with negative margins. The Ki-67 index was 2%+ (G1 according to the 2019 WHO classification). The patient recovered uneventfully, and a 3-month follow-up CT showed no signs of recurrence or metastasis.

CONCLUSION

This case suggests that simple appendectomy with close surveillance might be considered as an individualized strategy for selected patients with intermediate-risk G1 tumors measuring 1-2 cm with serosal or perineural invasion but without lymphovascular invasion and with negative margins. However, further validation with larger studies and longer follow-up is needed.