Why Adnexal Masses Occur in GI Malignancies
Gastrointestinal malignancies can metastasize to the ovaries, creating adnexal masses that may be solid or cystic, and must be distinguished from primary ovarian cancers and incidental benign lesions. 1
Mechanisms of Adnexal Mass Formation in GI Malignancies
Metastatic Disease to the Ovaries
Solid adnexal masses in patients with known GI malignancy are more likely to represent metastases, though metastases can also present as predominantly cystic lesions, making differentiation challenging. 1
The ovaries are a common site for metastatic spread from gastrointestinal primary tumors, particularly gastric, colorectal, and appendiceal cancers (Krukenberg tumors being the classic example from gastric primaries). 1
Metastatic deposits reach the ovaries through several routes:
- Hematogenous spread via arterial or venous circulation
- Lymphatic dissemination through retroperitoneal lymphatic channels
- Transcoelomic seeding across the peritoneal cavity
- Direct extension from adjacent bowel structures 1
Mimicry by Primary GI Tumors
Appendiceal tumors, particularly mucinous neoplasms, can directly mimic adnexal masses and remain undiagnosed until surgery, as they may be asymptomatic and present with non-specific clinical, laboratory, and radiologic findings. 2
Large appendiceal masses can be mistaken for right adnexal pathology even with advanced imaging methods like MRI, because of their anatomic proximity to the right ovary and fallopian tube. 2
Diagnostic Approach to Differentiate Etiology
Initial Imaging Strategy
Transvaginal ultrasound combined with color Doppler remains the first-line imaging modality to characterize any adnexal mass, even in patients with known GI malignancy, as it can distinguish benign from malignant features with >90% sensitivity. 3
Ultrasound features suggesting metastatic disease include solid components, thick septations (>2-3 mm), bilaterality, Doppler flow to solid components, and presence of ascites. 4
Advanced Imaging for Problem-Solving
MRI pelvis with IV contrast is the problem-solving modality of choice when ultrasound cannot definitively characterize the mass origin or distinguish between metastatic disease, primary ovarian cancer, and benign entities. 5, 3, 6
MRI can identify specific benign entities such as endometriomas (high T1, low T2 signal), fibromas, and peritoneal inclusion cysts that may be incidentally discovered in cancer patients. 1
CT abdomen and pelvis with IV contrast should be obtained for staging purposes when malignancy is suspected, but CT should not be used for initial mass characterization as it provides inferior tissue characterization compared to ultrasound and MRI. 3, 1
Role of Tumor Markers
- CA-125 should not be relied upon as a standalone test to distinguish metastatic GI disease from primary ovarian cancer, as it performs worse than ultrasound and may be elevated in both conditions or falsely low in borderline and low-grade malignancies. 3, 6
Clinical Pitfalls to Avoid
Do not assume all adnexal masses in cancer patients represent metastatic disease: even in postmenopausal women with known malignancy, approximately 70% of adnexal masses are benign, including simple cysts (17-24% frequency), fibroids, and endometriomas. 7, 8
Always identify both ovaries separately on imaging to avoid mistaking pedunculated uterine fibroids (present in 20-30% of postmenopausal women) for ovarian masses, and trace vascular supply to confirm origin. 7, 6
Recognize that appendiceal tumors must be kept in mind when evaluating right-sided adnexal masses in patients with GI symptoms, as they can be indistinguishable from ovarian pathology on imaging. 2
Ensure gynecologic oncology consultation for suspicious masses, as only 33% of women with eventual ovarian cancer diagnosis receive appropriate subspecialty referral, yet this is the second most important prognostic factor after stage. 3