AIM: To investigate the prevalence and implications of unusual histopathological findings in appendectomy specimens from patients with suspected acute appendicitis. METHODS: The demographic and histopathological data of 1621 patients (≥ 16 years-old) who underwent appendectomy to treat an initial diagnosis of acute appendicitis between January 1999 and November 2011 were retrospectively assessed. Microscopic findings were used to classify the patients under six categories: appendix vermiformis, phlegmonous appendicitis, gan- grenous appendicitis, perforated appendicitis, supurative appendicitis, and unusual histopathologic findings. The demographic and clinicopathologic characteristics of patients with unusual histopathologic findings were evaluated in detail, and re-analysis of archived resected appendix specimens was carried out. RESULTS: A total of 912 males and 709 females, from16 to 94 years old, were included in the study and comprised 789 cases of suppurative appendicitis, 370 cases of appendix vermiformis, 243 cases of perforated gangrenous appendicitis, 53 cases of flegmaneous appendicitis, 32 cases of gangrenous appendicitis, and 134 (8.3%) cases of unusual histopathological findings. The unusual histopathological findings included fibrous obliteration (n = 62), enterobius vermicularis (n = 31), eosinophilic infiltration (n = 10), mucinous cystadenoma (n = 8), carcinoid tumor (n = 6), granulomatous inflammation (n = 5), adenocarcinoma (n = 4; one of them mucinous), and mucocele (n = 3), adenomatous polyp (n = 1), taenia sup (n = 1), ascaris lumbricoides (n = 1), appendiceal diverticula (n = 1), and B cell non-hodgkin lymphoma (n = 1). None of the 11 patients with subsequent diagnosis of tumor were suspected of cancer prior to the appendectomy. CONCLUSION: Even when the macroscopic appearance of appendectomy specimens is normal, histopathological assessment will allow early diagnosis of many unusual diseases.
