Appendiceal endometriosis with intestinal metaplasia is particularly challenging to diagnose preoperatively based on clinical features. Microscopically, it can mimic malignant transformation into mucinous neoplasms of the appendix. The present study reports a case of a 47-year-old woman who presented with abdominal pain that was not related to her menstruation. The preoperative diagnosis and laparoscopic evaluation were chronic appendicitis. No mucinous or haemorrhagic secretions were present within the abdominal cavity. Pathological evaluation revealed conventional endometriosis with intestinal-type metaplasia of the epithelium. An inverse pattern of cytokeratin (CK)7, paired-box 8, estrogen receptor, CK20, caudal type homeobox transcription factor 2 and mucin 2 immunoreactivity between intestinal-type and endometrial-type endothelium was observed. Infiltration and replacement of the appendiceal wall by marked levels of acellular mucin, a lack of stromal components and a DNA mismatch repair protein profile were vital in diagnosing appendiceal endometriosis without appendiceal mucinous neoplasms (AMNs). The lesion of appendiceal endometriosis are usually superficial and small in previously reported cases but was deeply invasive in our case. A careful histopathological examination is necessary for diagnosing and distinguishing the histologic imitators of AMN.
Keywords: appendiceal mucinous neoplasm; appendix; endometriosis; intestinal metaplasia.
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