A Krukenberg tumor is a type of ovarian tumor which starts in another area of the body and migrates to the ovaries. Around five to six percent of ovarian cancers present as Krukenberg tumors, and the prognosis for patients with this type of tumor is not good.
Because these tumors are secondary metastases, rather than primary tumors, identifying one means that a patient has an underlying primary cancer which may have spread to other areas of the body, which would complicate treatment considerably.
These tumors can arise from malignant cells in any mucin-secreting area of the body.
The tumor is known as an adenocarcinoma, a reference to the fact that it originates in glandular tissue, and cancers of the breast and gastrointestinal tract are most likely to give rise to a Krukenberg tumor.
Historically, people thought that the cancer cells drifted across the abdomen to the site of the ovaries, but there is evidence that they can be carried in the blood or lymph as well.
When a Krukenberg tumor is examined by a pathologist, specialized cells known as signet ring cells are seen.
These cells are so filled with mucin that the nucleus of the cell is pushed to one side, and they do vaguely resemble signet rings, hence the name.
An alternate name for this type of tumor is a signet ring cell carcinoma; such cancerous tumors can also be found in other areas of the body.
Krukenberg tumour, also referred to as a carcinoma mucocellulare, refers to the “signet ring” subtype of metastatic tumour to the ovary.
The colon and stomach are the most common primary tumours to result in ovarian metastases, followed by the breast, lung, and contralateral ovary.
The tumours represent 5-10% of all ovarian tumours and upto 50% of all metastatic tumours to the ovary. The estimated incidence of Krukenberg tumour is at approximately 0.16/100.000 per year 7.
They tend to develop during the reproductive years 4-5.
Abdominal or pelvic pain, abdominal bloating, or pain during intercourse, may be the presenting symptom. Irregular bleeding may also be seen.
Pathology and pathophysiology
Krukenberg tumours are metastatic tumours to the ovary that contain well defined histological characteristics – mucin-secreting “signet ring” cells and usually originate in the gastrointestinal tract 4.
The time from diagnosis of the primary neoplasm to the development of ovarian metastasis is variable, and can range from several months to > 10 years.
Cytologic examination often reveals mucoid degeneration and many large cells shaped like signet rings.
They can originate from:
- stomach cancer (signet-ring cells): most common
- colorectal carcinoma: second most common
- breast cancer
- lung cancer
- contralateral ovarian carcinoma
- pancreatic carcinoma
- cholangiocarcionoma/gallbladder carcinoma
Most imaging features are non-specific, consisting of predominantly solid components or a mixture of cystic and solid areas. It is often difficult to differentiate from other ovarian neoplasms 4-5.
There are a variety of metastatic carcinomas to the ovary that can mimic primary ovarian tumours 4.
These tumour are typically seen sonographically as bilateral, solid ovarian masses, with clear well defined margins. An irregular hyper-echoic solid pattern and moth eaten like cyst formation is also considered a characteristic feature 7.
CT appearances can be indistinguishable from primary ovarian carcinoma 2. Features will favour towards a Krukenberg tumour if a concurrent gastric or colic mural lesion is seen.
There is some evidence that tumours originating from the stomach may be denser on contrast enhanced CT than those originating from the colon 3.
The great majority of Krukenberg tumours are signet-ring cell carcinomas arising in the stomach. Signet-ring cells scatter in the ovarian stroma with abundant collagen formation or marked oedema.
Therefore, Krukenberg tumours can occasionally show low or high signal intensity on T2-weighted images 6.
Krukenberg tumours may demonstrate some distinctive findings on MRI, including:
- bilateral complex masses with hypo-intense solid components (dense stromal reaction) 4-5
- internal hyperintensity (mucin) on T1 and T2 weighted MR images 4
- Strong contrast enhancement is usually seen in the solid component or the wall of the intratumoural cyst 6.
Treatment and prognosis
Differentiation between primary and metastatic ovarian carcinoma is of great importance with respect to treatment and prognosis, but may be very difficult based upon imaging findings solely.