Can a 3cm left adnexal mass with central hemorrhage and peripheral vascularity, and a normal beta human chorionic gonadotropin (hCG) level, be endometriosis of the fallopian tube, and what are the other possible differentials?

Differential Diagnosis of 3cm Left Adnexal Mass with Central Hemorrhage and Peripheral Vascularity

Primary Diagnosis: Ectopic Pregnancy Must Be Excluded First

This presentation is highly concerning for tubal ectopic pregnancy and must be managed as such until definitively ruled out, regardless of the low beta-hCG level. 1

The combination of an extraovarian adnexal mass with central hemorrhagic component and peripheral vascularity in the absence of an intrauterine pregnancy creates a high likelihood of ectopic pregnancy, even with beta-hCG of 0.3 mIU/mL. 1 Approximately 22% of ectopic pregnancies occur at hCG levels below 1,000 mIU/mL, and ectopic pregnancy can occur at any hCG level. 2, 3

Critical Diagnostic Steps:

• Confirm the mass is extraovarian using the "sliding sign" technique with gentle transvaginal transducer pressure to determine if the mass and ovary move independently. 1

• Assess for "claw sign" of ovarian parenchyma partially surrounding the mass—if present, this favors corpus luteum over ectopic pregnancy. 1

• Evaluate echogenicity: A hyperechoic rim favors tubal ring (ectopic), while hypoechoic appearance favors corpus luteum. 1

• Document presence or absence of intrauterine pregnancy—absence with an adnexal mass creates a positive likelihood ratio of 111 for ectopic pregnancy. 1

• Assess for free intraperitoneal fluid—echogenic fluid suggests hemoperitoneum from ruptured ectopic or hemorrhagic cyst. 1

Alternative Differential Diagnoses

1. Hemorrhagic Corpus Luteum Cyst (Most Likely Benign Alternative)

The combined sonographic characteristics of central hemorrhage (spiderweb-appearing or retracting clot) and peripheral vascularity are diagnostic of a hemorrhagic cyst. 4

• Hemorrhagic corpus luteum typically appears as a <3 cm cystic lesion with thick wall and may contain internal echoes or hemorrhage. 1
• Peripheral vascularity on color Doppler is characteristic of both hemorrhagic cysts and corpus luteum. 4, 1
• Luteal cysts with central hemorrhagic component and peripheral vascularity are classified as O-RADS 2 with <4% malignancy likelihood. 1
• The critical distinguishing feature from ectopic is whether the mass is inside or outside the ovary. 1

2. Endometrioma (Ovarian, Not Tubal)

True tubal endometriosis presenting as a 3cm mass is extremely rare; endometriomas are almost always ovarian in origin. 4

• Endometriomas characteristically show low-level internal echoes, mural echogenic foci, or nonvascular solid attenuating components on ultrasound. 4
• The described peripheral vascularity is atypical for endometriomas, which typically lack significant internal vascularity. 4
• Endometriomas can undergo decidualization in pregnancy and develop vascularized papillary projections, but this patient's beta-hCG is essentially negative. 4

3. Tubal Pathology (Other Than Ectopic)

• Hydrosalpinx: Appears as tubular cystic mass with or without folds, but typically lacks the central hemorrhage and peripheral vascularity described. 4
• Tubal torsion: Could present with hemorrhage, but would typically show absent or decreased flow on Doppler, not peripheral vascularity. 4

4. Other Ovarian Lesions

• Dermoid cyst (mature cystic teratoma): Shows echogenic attenuating component or small horizontal interfaces, not central hemorrhage with peripheral vascularity. 4
• Ovarian torsion with massive ovarian edema: Would show enlarged ovary with peripheral follicles and decreased or absent central flow. 4

Management Algorithm

If Patient is Hemodynamically Stable:

1. Obtain serial beta-hCG measurements every 48 hours to assess for appropriate rise or fall. 1, 2

2. Repeat transvaginal ultrasound in 48-72 hours if initial hCG is below discriminatory threshold. 1, 2

3. Monitor for warning signs: If hCG plateaus (<15% change over 48 hours) or rises abnormally (>10% but <53% over 48 hours), suspect abnormal pregnancy. 2

4. If hCG rises appropriately (doubles every 48-72 hours) and repeat ultrasound confirms intrauterine pregnancy, the adnexal mass is likely a corpus luteum. 1, 2

5. If mass proves to be corpus luteum in premenopausal woman and <5 cm: No additional management required. 1

If Ectopic Pregnancy is Confirmed or Highly Suspected:

• Immediate gynecology consultation for consideration of medical management (methotrexate) versus surgical management. 3, 5

Critical Pitfalls to Avoid

• Never exclude ectopic pregnancy based solely on negative or low beta-hCG in a woman of reproductive age with an adnexal mass. 1, 2

• Do not rely on color Doppler alone to differentiate tubal ring from corpus luteum—both demonstrate peripheral vascularity. 1

• Do not perform fine-needle aspiration of adnexal masses due to risk of seeding if malignancy is present. 1

• Avoid premature diagnosis of nonviable pregnancy based on a single low hCG value—serial measurements are essential. 2

• Do not wait longer than 48-72 hours between hCG measurements in hemodynamically stable patients with pregnancy of unknown location. 2