Cystic Teratoma of the Ovary

John Walter Millstine, MD - Case Coordinator
Mylinh D Huynh, MD - Radiology Discussion
Gerald P Bailey, MD, PhD - Pathology Discussion
Pablo R Ros, MD, MPH - Attending Radiologist

June 10, 2002

Presentation

Imaging Findings

On computed tomography (CT) images, dilated, fluid-filled loops of small bowel are evident. The transverse colon appears fairly normal, although there may be some fluid in the lumen. The third image of this initial study demonstrates significant thickening of the small bowel wall. These findings are indicative of a diffuse process, such as obstruction, infection, or, less likely, ischemia.

The patient was sent to the operating room for relief of the small bowel obstruction. Findings at surgery led to additional (pelvic) imaging.

Axial pelvic CT images show a well-defined mass to the left of midline. The mass is characterized by calcifications and a large percentage of fat density. There is no evidence of adenopathy. Given the fat component and calcifications, the most likely diagnosis is a dermoid tumor or teratoma of the left ovary.

Diagnosis

Discussion

First specimen: distorted ovary with an 8.5-cm mass with a cheesy, yellow appearance. The presence of hairs is diagnostic for dermoid cyst. On microscopic images, squamous cell carcinoma is visible diffusely throughout the cyst. It ranges from poorly differentiated to well differentiated with keratin formation. There were no other ectodermal, mesodermal, or endodermal components within the cyst, besides the hair, sebaceous glands, skin, and squamous cell carcinoma. From a pathological standpoint, this is a cystic teratoma with squamous cell carcinoma arising within the ectodermal component.

Radiology Discussion

Teratoma is a neoplasm of germ cell tumors arising along the line of migration of the primordial germ cells. This tumor is composed of elements of all 3 germ layers. Ectodermal tissue is the most abundant, and typically manifests in the form of squamous epithelium, brain tissue, glia, retina, choroid plexus, and/or ganglia. Mesodermal tissue typically gives rise to bone and/or cartilage. Endodermal tissue may form bronchial and gastrointestinal epithelium, thyroid glands, and/or salivary glands. The World Health Organization has defined three categories of teratoma: mature (90% of all cases), immature, and monodermal. Monodermal teratomas are highly specialized; examples include struma ovarii (thyroid cells and function) and carcinoid.

Mature cystic teratomas represent up to 30% of all ovarian neoplasms. They present most commonly during the reproductive years and are bilateral in 8-15% of cases. These tumors are typically (60%) 5-10 cm, though specimens up to 50 cm have been reported. Mature teratomas are generally benign, but the tumor undergoes malignant transformation in 1-2% of cases. Immature teratomas, however, are typically malignant. This is the second most common malignant ovarian neoplasm. The majority of these tumors (75%) are found in women in their 20s They are rarely bilateral and grow very quickly, so pain is a common presenting symptom. Complications associated with ovarian teratoma include torsion, infection, rupture and malignant transformation.

The following imaging findings may be indicative of teratoma:

• X-Ray: Soft tissue mass containing calcification (such as teeth)
• Ultrasound: Echogenic mass with inner mural components (hair, sebum) and acoustic shadow (calcium, teeth); cysts with mural echogenic mass (Rokitansky’s protuberance); fat/ fluid level.
• CT: Soft tissue mass with fat/ fluid level attenuation and calcification/ossification (teeth, bone).
• MR: Fluid/fluid level; fat

CT is the best modality for differentiating the various components of a teratoma.

Malignant transformation of a mature teratoma occurs in less than 2% of cases. The most common malignant transformation (80%) produces squamous cell carcinoma, because squamous tissue is typically the most abundant. Adenocarcinoma accounts for 7% of malignant transformations, while sarcoma and melanoma are much more rare. Malignant transformation should be suspected in patients older than 45 years and in cases with tumors larger than 10 cm. Symptoms that may indicate malignant transformation are pain, abdominal distention, ascites, constipation, diarrhea, micturition, and dyspareunia. Laboratory test results, such as a CA 125 level greater than 35 U/mL or the presence of the SCC antigen (76% sensitivity), can also confirm malignant transformation. It is difficult to define imaging characteristics for malignant transformation, since it is such a rare entity. On CT, the presence of a dermoid plug larger than 5 cm with a "cauliflower" appearance and irregular border at an obtuse angle to the inner wall of the cyst may suggest malignant changes. Some studies in China have suggested that exceptionally low resistance index (<0.4) and plasticity index (<0.6) on ultrasound may also be indicative of transformation.

Malignant ovarian teratoma is typically staged by histology, although the presence of ascites, pleural effusion, lymphadenopathy, and liver or lung metastases can be instructive. Treatment is typically surgical (e.g., total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, pelvic lymphadenectomy) with adjuvant radiation and chemotherapy (5FU/Cisplastin) in advanced cases.

References

Kikkawa F, et al. Diagnosis of squamous cell carcinoma arising from mature cystic teratoma of ovary. Cancer. 1998; 82(11):2249-55.

Ramachandran KN, et al. Osteosarcoma arising in a mature cystic teratoma of the ovary: A case report. Indian Journal of Radiology Imaging. 1999; 9(2):65-67.

Cavenail et al. Ovarian teratoma with high level of differentiation. Southern Medical Journal. May 2001; 94(5).

Emoto M, et al. Transvaginal color Doppler ultrasonic characterization of benign and malignant ovarian cystic teratomas and comparison of serum squamous cell carcinoma antigens. Cancer. 2000; 88(10):2298-304.

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