Differential Diagnosis for a 21-year-old Woman with a Left Adnexal Mass
Single Most Likely Diagnosis
- Dermoid cyst: This is the most likely diagnosis due to the patient's age and the description of the mass as a 5-cm echogenic, complex mass in the left adnexa. Dermoid cysts are common in young women and can appear as complex masses on ultrasonography due to their potential to contain a variety of tissues such as hair, teeth, and bone.
Other Likely Diagnoses
- Mucinous cystadenoma: Although less common than dermoid cysts, mucinous cystadenomas can present as complex adnexal masses. They are typically benign but can grow quite large.
- Ovarian thecoma: Thecomas are ovarian stromal tumors that can present as solid or complex masses. They are less common than dermoid cysts but should be considered in the differential diagnosis of an adnexal mass.
- Corpus luteum cyst: Given the patient's regular menstrual cycles and the absence of other symptoms, a corpus luteum cyst is less likely but still possible. These cysts are usually functional and resolve on their own.
Do Not Miss Diagnoses
- Serous cystadenocarcinoma: Although less likely in a young woman, ovarian cancer must be considered in the differential diagnosis of any adnexal mass. It is crucial to rule out malignancy, especially if the mass has suspicious features on imaging or if there are other concerning symptoms or risk factors.
- Ectopic pregnancy: Despite the negative urine pregnancy test, ectopic pregnancy is a critical diagnosis to consider in any sexually active woman with an adnexal mass, due to its potential for severe morbidity and mortality. However, the regular menstrual cycles and negative pregnancy test make this less likely.
Rare Diagnoses
- Other rare ovarian tumors: Such as ovarian fibromas, Brenner tumors, or sex cord-stromal tumors, which can present as adnexal masses but are less common.
- Adnexal torsion or other non-neoplastic conditions: Although the mass is described as non-tender, conditions like adnexal torsion or other non-neoplastic masses (e.g., endometriomas, tubo-ovarian abscesses) should be considered, especially if the patient's presentation changes or if there are other symptoms.