Appendiceal diverticulitis clinically masquerading as an appendiceal carcinoma

Appendiceal diverticulosis is a rare condition. Herein reported is a case of appendiceal diverticulosis and diverticulitis clinically masquerading as appendiceal carcinoma. A 62-year-old woman presented with abdominal pain. US and CT showed a tumor measuring 5 × 4 × 4 cm in vermiform appendix. Colon endoscopy showed mucosal elevation and irregularity in the orifice of vermiform appendix. A biopsy of the appendiceal mucosa showed no significant changes. Clinical diagnosis was appendiceal carcinoma and wide excision of terminal ileum, appendix, cecum, and ascending colon was performed. Grossly, the appendix showed a tumor measuring 5 × 3 × 4 cm. The appendiceal lumen was opened, and the appendiceal mucosa was elevated and irregular. The periappendiceal tissue showed thickening. Microscopically, the lesion was multiple appendiceal diverticula. The diverticula were penetrating the muscle layer. The mucosa showed erosions in places. Much fibrosis, abscess formations, and lymphocytic infiltration were seen in the subserosa. Abscesses were also seen in the diverticular lumens. Some diverticula penetrated into the subserosa. The pathologic diagnosis was appendiceal diverticulitis. When they encounter an appendiceal mass, clinicians should consider appendiceal diverticulitis as a differential diagnosis.