Ovarian dermoid cyst

Clinical History

Acute right lower quadrant pain.

Imaging Findings

This otherwise healthy patient was admitted with acute abdominal pain in the right lower quadrant.

Blood tests and abdominal radiographs were negative. A subsequent ultrasonogram of the abdomen revealed a bilobular lesion close to the right side of the uterine fundus (the anatomical position of the right ovary). The lesion had a fat-fluid level as well as a highly echogenic nodule with shadowing ("dermoid plug") , and showed no perfusion at CDS.

A CT scan of the abdomen showed a well-defined right adnexal cystic lesion, with two cavities containing fat and a fat-fluid level, and two rounded soft tissue densities. There was no contrast enhancement. A small quantity of free fluid was also noticed in the rectouterine pouch.

Discussion

Ovarian dermoid cysts (which form 20% of all ovarian tumours) are germ cell tumours and are also called mature or benign teratomas. These neoplasms are invariably benign and are presumably derived from the ectodermal differentiation of totipotent cells. They are usually found in young women during the active reproductive years. They are bilateral in 10-15% of cases. Characteristically, they are unilocular, or rarely multilocular, cysts that have a thin wall lined by apparent epidermis. From this epidermis, hair shafts frequently protrude. Within the wall, it is common to find tooth structures and areas of calcification. The lumen of the cyst is filled with a sebaceous secretion that is admixed with strands of hair. Complications include torsion and rupture. Torsion is the most common complication, whereas rupture is uncommon and leads to chemical peritonitis.

Sonographically, dermoid cysts have a variable appearance ranging from completely anechoic to completely hyperechoic. Features considered specific are: a)a cystic mass with an echogenic mural nodule, called "dermoid plug", which contains hair, teeth or fat and produces a posterior acoustic shadowing, b) a mixture of matted hair and sebum that is highly echogenic because of multiple tissue interfaces, and it produces ill-defined acoustic shadowing that obscures the posterior wall of the lesion ("tip of the iceberg" sign)and c)a fat-fluid level is commonly seen if the viscid contents are given time to layer. Strongly echogenic dental elements are often seen in the periphery. On CT the fat content and the well-defined cystic appearance is highly specific. Whereas most benign cystic teratomas contain some soft tissue components, the presence of a large (>10cm), irregular soft tissue mass within the tumour should raise the suspicion of malignant transformation.

Differential Diagnosis List

Final Diagnosis

Dermoid cyst

URL:	https://www.eurorad.org/case/1696
DOI:	10.1594/EURORAD/CASE.1696
ISSN:	1563-4086