A Krukenberg tumor is the name given to tumors of the ovaries. Although they may appear to be a primary tumor of the ovary, they are always a metastasis (i.e. a secondary tumor) which has spread from a malignant tumor that arose in the gastrointestinal tract. Krukenberg tumors are often found in both ovaries. Microscopically, they are characterized by appearance of mucin-secreting signet-ring cells in the tissue of the ovary.

The Krukenberg tumor is classically a metastatic signet ring cell adenocarcinoma arising in the stomach and metastasizing to the ovaries. Other primary sites have been described such as colon, gallbladder, bile ducts or appendix and a few cases have no detectable primary. They are usually large, bilateral and associated with a poor prognosis.

Metastatic cancer of the ovary accounts for only about 5% of ovarian cancer; in the remainder, the ovary is the primary cancer site. Krukenberg tumors are the third most common metastatic ovarian cancer (after epithelial and germ-cell tumors) and make up 14% of these cancers.

The exact mechanism of metastasis of the tumour cells from the stomach, appendix or colon to the ovaries; classically it was thought that direct seeding across the abdominal cavity accounted for the spread of this tumor, but recently some researchers have suggested that lymphatic (i.e. through the lymph nodes), or haematogenous (i.e. through the blood) spread is more likely, as most of these tumours are found on the inside of the ovaries.

CT/MRI frequently demonstrate bilateral solid masses with well demarcated intratumoral cysts, with walls of the cyst demonstrating intense enhancement. Less commonly, they are enhancing solid masses without intratumoral cysts. Rarely present as predominantly cystic masses. Solid masses can degenerate and show central necrosis. MRI sequences frequently demonstrate hypointense solid components within bilateral ovarian masses on T2-weighted images.