The varied aspects of spread of
appendiceal neoplasms are reviewed with emphasis on the often clinically dramatic phenomenon known as
pseudomyxoma peritonei, a term mostly used to describe grossly evident
mucin within the peritoneal cavity. The majority of cases of
pseudomyxoma peritonei result from
tumors primary in the appendix, which are usually low-grade. On microscopic examination
pseudomyxoma peritonei is typically characterized by large aggregates of
mucin which may be relatively acellular or cellular containing strips of mucinous epithelium, mucinous epithelium encircling glands and
cysts, or aggregates of mucinous epithelium lying within
mucin pools. High-grade
adenocarcinoma of the appendix may spread to the omentum and peritoneal surfaces without grossly striking
mucin deposition and resemble spread of other high-grade gastrointestinal
adenocarcinomas. In many cases of
pseudomyxoma peritonei in females there is involvement of one, or more often, both ovaries. The size of the
ovarian neoplasms characteristically dwarfs the often relatively unremarkable appearing appendix in these cases. The ovaries are typically multilocular, although one locule may dominate, and in cases in which the primary is a low-grade appendiceal
mucinous neoplasm often have a "jelly-like" consistency. In cases of spread of frank
adenocarcinomas the ovarian
metastases typically have a more solid, albeit still somewhat gelatinous consistency. Microscopic examination of the ovaries typically shows surface involvement, a characteristic of spread to the ovaries in general, and the glands and
cysts that replace most or all of the parenchyma are typically lined by tall
mucin-rich cells with, in many cases, relatively bland microscopic features. In cases of frank
adenocarcinoma, the
tumors may mimic closely a primary
mucinous adenocarcinoma of the ovary. Spread to the ovaries may also be seen in cases of frank intestinal-type
adenocarcinoma primary in the appendix and the uncommon
signet ring cell carcinoma of the appendix, the latter being one cause of the
Krukenberg tumor. Occasional cases are reported in the literature of ovarian spread of
goblet cell carcinoid tumor of the appendix, but in our opinion most of the primary
tumors in those cases are better classified as
adenocarcinomas, usually dominantly of signet-ring cell type, albeit sometimes with focal neuroendocrine differentiation. Other interesting aspects of spread of
appendiceal neoplasms include to the lining of the uterus and the fallopian tube. In yet other cases the
tumors may present clinically as incidentally discovered mucinous aggregates within
hernia sac specimens or as a scrotal mass.