Differential Diagnosis for Gradually Enlarging Abdominal Mass in Young Women

Key Clinical Context

The American College of Radiology recommends considering a solid or cystic mass rather than fluid accumulation in cases of slowly enlarging abdomen over months, as ascites typically presents over weeks, not months to years 4

The American College of Radiology suggests that ovarian cystadenomas are the leading consideration for large abdominal masses in young women, as they are common benign ovarian neoplasms that can present as large abdominal masses and may reach enormous sizes over months 1, 2
The American College of Radiology recommends considering mature cystic teratomas (dermoid cysts) as a high differential diagnosis for persistent ovarian masses in young women, as up to 70% of adnexal lesions in young women are functional cysts that resolve spontaneously, but persistent masses over 9 months are more likely dermoids or cystadenomas 1

The American College of Radiology recommends beginning with combined transabdominal and transvaginal ultrasound with Doppler evaluation as the first-line imaging modality for all abdominal masses in women of reproductive age, to determine if the mass is solid or cystic, assess vascularity and relationship to surrounding structures, and identify the organ of origin 1, 2, 7
The American College of Radiology suggests obtaining age-appropriate tumor markers, including CA-125 for epithelial ovarian neoplasms, and AFP and hCG for germ cell tumors in women under 35 years 1, 2, 8

The American College of Radiology recommends proceeding to MRI pelvis with and without IV contrast if ultrasound findings are indeterminate, as MRI is superior to CT for characterizing complex adnexal masses and provides 91% overall accuracy for diagnosing malignancy 2, 7

The American College of Radiology notes that the incidence of malignancy in adnexal masses in reproductive-age women is low (approximately 3.6-10.7% for indeterminate lesions), but certain features warrant heightened concern, including solid components with internal vascularity, papillary projections, ascites, and rapid growth 1, 2, 7
The British Journal of Cancer recommends considering gastrointestinal and soft tissue sources for pelvic masses, particularly with upper abdominal location, and avoiding fine-needle aspiration for suspected ovarian masses due to risk of malignant cell spillage 5