Interval Appendectomy Specimens: Potential Mimickers of Important Inflammatory and Neoplastic Conditions

Abstract

Context.—Patients with perforated appendicitis are often managed with antibiotic therapy followed by a delayed appendectomy. Histologic features of such specimens have been incompletely described, especially in the recent literature. Objective.—To describe the histomorphology of interval appendicitis with a focus on features that could mimic important conditions, such as infections, Crohn disease, and mucinous neoplasms. Design.—Histologic evaluation of 100 interval appendectomy specimens with clinical and radiologic correlation. Results.—A total of 54 of the 100 patients (54%) had radiologic evidence of appendiceal perforation, and 97% were treated with intravenous and/or oral antibiotic therapy prior to appendectomy. Percutaneous drains were placed in 34 cases (34%). Common histologic findings included mural eosinophilic infiltration (54%), periappendiceal fibrosis (54%), and xanthogranulomatous inflammation (31%). Periappendiceal fibrosis was frequent among patients with radiologic evidence of perforation. Nine cases (9%) featured pulse granulomata associated with fecal material. Epithelioid granulomata were detected in 6% of cases and were confined to mucosal lymphoid follicles in all cases. Only 4 of these were accompanied by mural lymphoid aggregates that raised the possibility of Crohn disease. Changes mimicking mucinous neoplasms were more common: 14% of cases (14 of 100) displayed goblet cell hyperplasia, 15% (15 of 100) contained diverticula, and 16% (16 of 100) showed mural or periappendiceal mucin pools. Conclusions.—Although interval appendectomy specimens occasionally contain inflammatory infiltrates that mimic infections and/or Crohn disease, changes that can be confused with mucinous neoplasms are more frequently encountered.