Abstract
Appendix vermiform from a 68-year-old man presenting with low-grade appendiceal mucinous neoplasm (mucinous cystadenoma; A). In periappendicular mucinous lakes (B), we observed groups of fluctuating cells, with large cytoplasmic vacuoles containing mucus (C). As judged by their immunohistochemical profile (CK−/CD68+; D,E), they represent histiocytes, not to be mistaken for signet-ring adenocarcinoma cells.