Adnexal Mass Differential Diagnosis

The differential diagnosis for an adnexal mass can be organized into the following categories:

• Single Most Likely Diagnosis
  • Ovarian Cyst: This is the most common cause of an adnexal mass, particularly in women of reproductive age. Ovarian cysts can be either benign (such as follicular cysts or corpus luteum cysts) or malignant. The likelihood of malignancy increases with age.
• Other Likely Diagnoses
  • Ectopic Pregnancy: Especially in women of reproductive age presenting with acute symptoms, an ectopic pregnancy should be considered, particularly if there is a history of assisted reproduction, previous ectopic pregnancy, or other risk factors.
  • Tubo-ovarian Abscess: This condition is an infectious process involving the fallopian tube and ovary, often resulting from pelvic inflammatory disease (PID). It presents with pain, fever, and sometimes an adnexal mass.
  • Endometrioma: Also known as a chocolate cyst, this is a type of ovarian cyst filled with old blood, occurring in women with endometriosis. It is more common in women of reproductive age with symptoms of endometriosis.
  • Dermoid Cyst (Mature Cystic Teratoma): A type of benign ovarian tumor that can contain several different types of tissues, such as hair, muscle, and bone. It is more common in younger women.
• Do Not Miss Diagnoses
  • Ovarian Torsion: Although not a mass per se, ovarian torsion can present with an adnexal mass if the torsion occurs around a pre-existing cyst or tumor. It is a surgical emergency.
  • Malignant Ovarian Neoplasm: While less common than benign ovarian cysts, malignant ovarian tumors are critical to identify early due to their high mortality rate if left untreated.
  • Ruptured Ectopic Pregnancy: A life-threatening condition that requires immediate surgical intervention.
• Rare Diagnoses
  • Paraovarian Cyst: A cyst that arises from the paraovarian tissue, which is separate from the ovary itself but can be adjacent to it.
  • Adnexal Torsion of a Paratubal Cyst: Similar to ovarian torsion but involves a cyst related to the fallopian tube.
  • Germ Cell Tumors: Such as dysgerminomas, which are rare types of ovarian cancer more commonly found in younger women.

Each diagnosis has a different set of risk factors, symptoms, and imaging characteristics that can help guide the differential diagnosis. Ultrasound is often the first-line imaging modality for evaluating adnexal masses, with further testing (such as MRI or CT scans) and tumor markers (like CA-125) used as needed based on the initial findings and clinical suspicion.