Unusual Histopathological Findings in Cases with a Preliminary Clinical Diagnosis of Acute Appendicitis: What was Expected, What Did We Discover?

Introduction: The most common cause of acute abdomen is appendicitis. Besides lymphoid hyperplasia and fecalith, less common lesions such as diverticulum, endometriosis, infectious agents, preneoplastic and neoplastic lesions are also in the etiology of acute appendicitis. Our aim is to document the findings after histopathological examination of appendectomy materials and to detect the lesions, which we call other diagnoses. Methods: The findings were divided into four groups as acute appendicitis, perforated appendicitis, lymphoid hyperplasia and "other diagnosis" in the appendectomy materials. Other diagnoses were also divided into two subgroups: Group 1 consisted of cases of acquired and anatomical abnormalities, chronic appendicitis, infectious agents and miscellaneous lesions. Group 2 consisted of serrated lesions, carcinomas, neuroendocrine neoplasia, mesenchymal tumor and secondary neoplasia. Results: Our study was conducted in 4,335 appendectomy materials and there were 562 (12.96%) cases in the "other diagnosis" group. Group 1 consisted of cases with diverticula (5.74%), fibrous obliteration (2.84%), skip lesion of ulcerative colitis (0.02), granulomatous inflammation (0.07%), enterobius vermicularis (0.55%), endometriosis externa (0.16%), and amyloid deposition (0.05%), while group 2 comprised cases with hyperplastic polyp (0.53%), sessile serrated adenoma (0.83%), low-grade mucinous neoplasia (0.28%), neuroendocrine cell proliferation (0.28%), neuroendocrine tumor (NET) (1.2%), gastrointestinal stromal tumor (0.02%), and secondary neoplasia (0.39%). Conclusion: In our study, most commonly, we detected diverticula and the most frequently found neoplastic lesion was NETs. Recently, due to the increased awareness of the presence of serrated lesions, the rate of diagnosis of these cases has also increased. In addition to neoplastic lesions detected because of histopathological examination of appendiceal materials, lesions characterized by parasitosis, endometriosis externa and granulomatous inflammation, as well as cases that require sustained treatment and follow-up will not be skipped. [ABSTRACT FROM AUTHOR]