Is Submucosal Lipomatosis of the Appendix Vermiformis Really a Rare Entity?

Background: Acute appendicitis (AA) is the most common surgical emergency in patients who visit the emergency department with abdominal pain. In some of the patients who were operated with a prediagnosis of AA, lymphoid hyperplasia, fecalitis, enterobius vermicularis, carcinoid tumor, or adenoma are determined without transmural inflammation in microscopic examination of the appendix. 'Submucosal lipomatosis' is also another entity that has been rarely reported in appendix localization. In this study, we aimed to determine the frequency and severity of submucosal fatty tissue (SFT) in appendectomy specimens and identify risk factors. Materials and Methods: 293 appendectomy specimens were evaluated retrospectively. The amounts of SFT (A0: None, A1: Isolated adipocytes (Mild), A2: Small adipocyte groups (Moderate), A3: Prominent adipocyte groups (Marked), A4: Severe adipocyte groups that narrow the lumen (Severe)) and the groups that were created according to the amounts of SFT (Group 1: Cases with A1,2,3,4, group 2: Cases with A2,3,4, group 3: Cases with A3,4) were determined in hematoxylin-eosin sections. Results: 91.47% of the cases had any amount of SFT. Amounts of SFT were mild in 23.89%, moderate in 46.76%, marked in 18.09%, and severe in 2.73%. All of the cases without SFT were in pediatric age. When the amount of SFT increased, the mean age and adult rate increased regularly (p<0.05). As 68% of the cases without SFT were female, male predominance was observed in cases with SFT. When the amount of SFT increased, male rate increased regularly (p<0.05). AA wasn’t determined in 26,28% of the cases. The AA rate in the group without SFT (20%) was marked lower than group 1 (78,73%), group 2 (82,32%), and group 3 (83,87%) (p<0.05). The most prominent increase in AA rate was between the group without SFT and group 1 which was the most sensitive group to the amount of SFT. When group 1,2,3 were compared, no significant increase in the AA ratio was found. Conclusions: The presence of SFT in the appendix is a common condition. Age increase and male gender are risk factors for the accumulation of SFT. Due to SFT accumulation increases the risk of AA, it would be logical to classify it as mild/moderate/marked/severe, and accept it as 'Submucosal lipomatosis'.