What is the single most appropriate tumor marker to request for a 60-year-old patient with lower abdominal discomfort, mild abdominal distension, and a nontender, solid irregular right adnexal mass?

Most Appropriate Tumor Marker for Solid Irregular Adnexal Mass in Postmenopausal Woman

CA 125 is the single most appropriate tumor marker to request for this 60-year-old postmenopausal woman with a solid irregular adnexal mass. 1

Rationale for CA 125 Selection

In postmenopausal women over 50 years old, CA 125 has a specificity of 98.5% when using a threshold of 35 U/mL, making it the primary tumor marker for suspected ovarian malignancy. 1 The clinical presentation—postmenopausal status, solid irregular mass characteristics, and absence of acute symptoms—strongly suggests potential ovarian cancer, for which CA 125 is the established first-line marker. 1

Key Clinical Features Supporting CA 125

• The solid irregular nature of this adnexal mass is a concerning feature for malignancy, as solid masses with irregular borders are among the ultrasound features most predictive of ovarian cancer. 2

• CA 125 should be measured before surgery in all patients with suspected ovarian cancer, according to established guidelines. 1

• CA 125 is elevated in approximately 80-90% of serous carcinomas, which represent the most common type of epithelial ovarian cancer. 1

Important Limitations to Recognize

CA 125 has a critical limitation: it only detects 50% of ovarian cancers in stage I, so a normal level does not exclude early cancer. 1 This is particularly important in this case, as the patient may still require surgical evaluation even if CA 125 is normal.

CA 125 results must be interpreted in conjunction with imaging findings, as false positives can occur in benign conditions including endometriosis, adenomyosis, pelvic inflammatory disease, and benign ovarian cysts. 1 However, in a postmenopausal woman (where these benign conditions are less common), the specificity is significantly higher.

When CA 125 Alone Is Insufficient

If CA 125 is not elevated, additional markers should be measured, particularly CA 19-9 for mucinous or clear cell tumors. 1 In young women, alpha-fetoprotein (AFP) and beta-HCG should be added to exclude germ cell tumors, though this is less relevant for a 60-year-old patient. 1

Integration with Imaging

CA 125 performs best when combined with ultrasound findings rather than used in isolation. 2 When the cutoff point of CA 125 is increased from 35 U/mL to 65 U/mL in the presence of resistive index <0.5 on Doppler ultrasound, specificity and positive predictive value both reach 100%. 2

CA 125 levels improve the specificity of diagnosing malignant ovarian tumors only in lesions already suspected to be malignant on ultrasound. 2

Why Not CEA?

CEA is not the appropriate first-line marker for adnexal masses. While CEA can be elevated in some ovarian cancers (particularly mucinous types), it is primarily used for gastrointestinal malignancies and is not the standard marker for evaluating suspected ovarian pathology. 1

Clinical Algorithm

1. Order CA 125 immediately as the primary tumor marker 1
2. Obtain transvaginal ultrasound with Doppler to characterize the mass morphology and vascularity 2
3. If CA 125 is elevated (>35 U/mL in postmenopausal women), this significantly increases suspicion for malignancy and warrants gynecologic oncology referral 1
4. If CA 125 is normal but imaging remains suspicious, consider additional markers (CA 19-9) and proceed with MRI for further characterization 2, 1
5. A progressively elevated CA 125 over time, even within the normal range, should prompt further evaluation as it may indicate malignancy 1