Accessory uterine cavities: a review of cases and an appeal for standard terminology.

Objective: To study and address the diagnostic, management, and classification challenges of unilocular myometrial cystic lesions adjacent to a normal uterine cavity.

Design: Describe 23 further cases, and undertake a systematic review using Medline, PubMed and Ovid for similar lesions.

Subjects: 23 cases of accessory uterine cavities presenting to pediatric and adolescent gynecologists in Australia and New Zealand.

Main Outcome Measures: 92 similar cases of cavitated myometrial masses were identified in the literature. The cases in our series and in the literature were examined for age at presentation, site of lesion, pathology, and presence of other anomalies.

Results: All patients in our series were aged ≤ 32 years. All presented with unilocular blood-filled myometrial lesions that did not communicate with the uterine cavity. All were located on the lateral aspect of the uterus in proximity to the round ligament. Of the 22 that have been resected, all were lined by endometrium and smooth muscle. These characteristics are mirrored in the previously described cases in the literature.

Conclusion: The frequency of these myometrial cystic masses is such that they can no longer be considered rare. Nevertheless, their etiology remains unclear. These lesions have often been given names suggesting that they are an early representation of adenomyosis. The alternative possibility of a Müllerian anomaly is supported by consistent anatomical location and young age of presentation in most reported cases. Yet the absence of documented associated anomalies raises concerns about this theory. To progress understanding of these lesions, consistent reporting of features including location and the presence or absence of other anomalies is required. In view of this ongoing uncertainty, we recommend the use of the term "accessory uterine cavity (AUC)." This terminology avoids the implication of either a pathological process or a congenital anomaly.