Myxoid degeneration of appendix wall: An entity in search of identity: Report of two cases.

Myxoid degeneration of the appendix wall without accompanying acute appendicitis (AA) is rare. We report two cases of myxoid degeneration of appendix associated with appendiceal adhesions. Both the cases showed marked splitting and disruption of smooth muscle fibers of muscularis propria by abundant myxoid ground substance and dispersed degenerated hypereosinophilic myofibers with pyknotic nuclei. Scattered degenerated myocytes with vacuolated cytoplasm were also identified. Focal serosal fibrosis was observed in both cases. We reviewed other pathologic processes that involve the appendix such as fibrous obliteration, AA, and appendiceal mucinous neoplasm (AMN) and conclude that the constellations of pathologic findings described herein are unique. Nonneoplastic dissecting myxoid degeneration of the appendix muscularis propria has not been reported in the pathology literature to date. The pathologic nature of appendiceal mucinous stromal change remains unclear; however, we hypothesize that the lesion occurs as a consequence of traction related injury to the appendix.