Findings: (Images 1 - 5)
The ultrasound images (1 and 2) demonstrate an echogenic mass in the left adnexa.. The differential diagnosis includes a hemorrhagic cyst, endometrioma, dermoid cyst, or a solid ovarian neoplasm. The MRI demonstrates a fat-fluid layer within the mass, which confirms the diagnosis of a dermoid cyst.

Discussion:
A dermoid cyst or cystic teratoma is a not uncommonly diagnosed adnexal mass. The mass contains all three of the germ cell layers. It typically contains fat and serous components and can also contain hair or teeth. The mass is typically heterogeneous on all MRI sequences, with the key to the diagnosis resting upon the identification of intrasubstance fat. Although the mass may be asymptomatic, surgical excision is recommended because of the increased incidence of infertility as well as the risk of rupture and torsion