Walthard nests, the solid or cystic proliferations of transitional epithelium, have been found in the subserosal tissue of 5.2% of surgically resected tubes (Hunt). They form from invagination of the tubal serosa followed by transitional metaplasia of the epithelium.

Walthard rests are solid or cystic aggregates of transitional cells located just beneath the serosa of the fallopian tube. They are thought to be invaginations of the serosal mesothelium that undergo transitional metaplasia. There is speculation that Brenner tumors of the ovary may arise via a similar process.1

Walthard rests are most common adjacent to the fimbria, but may be seen throughout the length of the tube. The cells are fusiform and occasionally exhibit longitudinal grooves typical of urothelial cells. Grossly, they are usually less than 1 mm in diameter.1,2

Excellent; benign entity that simply needs to be recognized by the pathologist.