Tumors that result from the metastasis of malignant tumors originating in other organs or tissues to the ovaries are referred to as ovarian metastatic tumors or secondary ovarian tumors. These comprise 5–10% of ovarian tumors. Common primary tumor sites include the breast, intestines, stomach, reproductive tract, and urinary tract. Ovarian Krukenberg tumors, also known as ovarian signet-ring cell carcinoma, are a specific type of metastatic adenocarcinoma originating from the gastrointestinal tract. These tumors are often bilateral, typically medium-sized, and may retain the original ovarian shape or appear kidney-shaped. On cross-section, they are mostly solid and gelatinous. Microscopically, the hallmark signet-ring cells are observed, characterized by nuclei displaced to one side of the cell and compressed against the cell membrane in a crescent shape by mucin, resembling a signet ring.
Pathways of Metastasis
The most common primary site is the gastrointestinal tract. The exact mechanisms of metastasis are not fully understood, but several possibilities are widely recognized:
- Hematogenous Spread: Ovarian metastatic tumors are more prevalent in younger individuals and premenopausal women, as richer ovarian blood supply before menopause is thought to facilitate hematogenous spread. Ovarian metastases are often part of systemic metastases from the primary tumor.
- Lymphatic Spread: The dense network of lymphatic drainage in the ovaries leads to retroperitoneal lymph nodes. In cases where cancer cells from the primary site infiltrate and metastasize to retroperitoneal lymph nodes, they may retrogradely reach the ovaries through lymphatic channels.
- Peritoneal Seeding: This theory, proposed earlier, states that cancer cells from the primary tumor can breach the serosal layer and detach into the peritoneal cavity or ascitic fluid. The movement aided by intestinal peristalsis and/or ascitic fluid allows these cells to seed on the ovarian surface and infiltrate. This is influenced by the ovaries' location in the lowest part of the abdominopelvic cavity and the physiological factors during ovulation, such as ovulation-related "defects" or epithelial invaginations that increase cancer cell seeding opportunities. However, many early-stage gastric cancers are also associated with ovarian metastases, and pathological evidence has shown that many metastatic ovarian lesions are deep within the ovary without involving the capsule. Therefore, metastasis to the ovary likely results from a combination of multiple pathways rather than a single mechanism.
Clinical Presentation
Symptoms lack specificity. Ovarian metastases may be discovered simultaneously with the diagnosis of the primary tumor or may present as a pelvic mass accompanied by abdominal pain, bloating, and ascites, while signs of the primary tumor may be minimal.
Treatment
Management of ovarian metastatic tumors depends on the location and treatment of the primary tumor and often requires a multidisciplinary collaboration. The treatment goal is symptom relief and control. If the primary tumor has been resected and there is no evidence of other metastases or recurrence, and if the ovarian metastasis is confined to the pelvic region, surgical resection of the lesion should be performed when feasible. Postoperative adjuvant therapy is then guided by the type of primary tumor. For the majority of ovarian metastatic tumors, treatment outcomes are poor, and the prognosis remains unfavorable.