Reactive lymphoid hyperplasia with a lipomatous component associated with fecal compaction in an appendiceal orifice

A 69-year-old man underwent endoscopic mucosal resection of a solitary polyp located in the cecum. After the procedure, a fecal mass and appendiceal orifice appeared under the cut surface. A diagnosis of reactive lymphoid hyperplasia was made based on the results of an immunostaining analysis, which revealed a segregated population of T cells and B cells in multiple lymphoid follicles. The aggregation of adipocytes forming a lipomatous area and granulation tissue was also observed. We speculate that the compaction of the fecal mass in the appendix triggered mucosal inflammation, resulting in the formation of the polyp, which concealed both the feces and appendiceal orifice.