Coexistence of Low Grade Appendiceal Mucinous Neoplasm and Endometriosis of the Appendix

Abstract Introduction/Objective Mucinous neoplasms of the appendix are rare malignancies, and most are found incidentally during surgery and subsequently diagnosed upon pathological examination. The prevalence is about 0.2-0.7%, and approximately one-third (3-34%) are low-grade mucinous neoplasms (LAMNs). Endometriosis is relatively rare in the appendix, accounting for 2.8% with prior history of endometriosis and 0.3% found incidentally in resected specimens. Rare cases of LAMN co-existing with endometriosis have been described in the literature. We report this case of a childbearing age female with the coexistence of LAMN and endometriosis with scarring of the appendix found intraoperatively during the laparoscopic removal of the endometriosis. Methods/Case Report A female of childbearing age presents to the hospital with complaints of heavy menses, dysmenorrhea, dyspareunia, and dyschezia during menstruation. The patient has a past medical history of endometriosis. With unsuccessful conservative treatment, the patient was advised to undergo laparoscopic excision of endometriosis. Incidental intraoperative sclerotic small appendix and fibrotic surrounding area was identified, leading to the suspicion of appendicitis likely due to previous recurrent episodes of endometriosis. The surgery was then extended to laparoscopic appendectomy. Histologically, the sections from the appendix showed areas of endometriosis surrounded by endometrial stroma (CD10 positive), also there was atypical glands in the muscularis layer with extra-appendiceal mucin. The glands were lined by cells with elongated nuclei, apical mucin and low-grade nuclear atypia. The patient was diagnosed with low-grade appendiceal neoplasm, extending to the mesoappendix with endometriosis. Results (if a Case Study enter NA) N/A Conclusion The coexistence of the LAMN and endometriosis is a rare entity. Intestinal metaplasia has been reported in some cases of endometriosis, and this may mimic LAMN. It is important to keep intestinal metaplasia of endometriosis in mind when diagnosing LAMN in an appendix with endometriosis. In our case, the presence of dysplasia, the absence of extensive decidualization, the extracellular mucin helped with the diagnosis.