Mesenteric origin hyalinized vascular pseudotumor mimicking duplicate acute appendicitis.

Appendiceal duplication is an exceptionally rare anomaly, with an incidence ranging from 0.004% to 0.009%. Most cases are asymptomatic and remain undetected on imaging, with diagnosis usually established incidentally during laparotomy performed for other intra-abdominal conditions. The differential diagnosis includes cecal diverticulum, mesenteric adenitis, epiploic appendagitis, and neoplasms of the colon or appendix. We report the case of a 22-year-old man whose preoperative findings and intraoperative appearance suggested appendiceal duplication. Histopathological examination, however, demonstrated acute appendicitis in one specimen and hyalinized vascular pseudotumor of mesenteric origin in the other. To the best of our knowledge, no prior reports describe this combination. This case highlights the diagnostic challenge posed by unusual mesenteric lesions that can mimic rare congenital anomalies such as appendiceal duplication. Awareness of such entities may prevent misinterpretation and contribute to a more accurate understanding of appendiceal pathology.