Ovarian Fibroma

Marc J Lee, MD - Case Coordinator
John Walter Millstine, MD - Radiology Discussion
Jason H Smouse, MD - Pathology Discussion
Pablo R Ros, MD, MPH - Attending Radiologist

March 10, 2003

Presentation

Imaging Findings

A transverse ultrasound image through the uterus demonstrates a solid mass abutting the endometrial stripe, and a sagittal image shows a 15-mm endometrial canal. There is some central hypoechoic fluid. There is some lobulation in the contour along the left aspect of the endometrial stripe and mass effect is apparent. The differential diagnosis at this point includes leiomyoma, leiomyosarcoma, or possibly an obstructive mass, such as simple fibroid, endometrioma, or adnexal mass arising from the ovary.

MR images show that the uterus is displaced posteriorly and to the left by the large, primarily hypointense soft tissue mass. The mass has central areas of hyperintensity. There appears to be a superior component to the mass, suggesting a bi-lobed, well-encapsulated lesion. Based on this appearance, primary uterine tumors would be excluded from the differential diagnosis. A normal right ovary is visible, but the left ovary is displaced posteriorly; so, this could be a complex mass arising from the left ovary. The differential diagnosis includes cystadenoma, endometrioma, ovarian metastasis, and cystadenocarcinoma. The post-contrast image shows some areas of enhancement, suggesting necrosis; there is not significant enhancement of the mass.

Differential Diagnosis

Diagnosis

Discussion

The gross sample is a 15-cm ovarian mass. Cystic degeneration is apparent on the cortical surface. The cut surface demonstrates a whorled, trabecular appearance; the mass is solid. There is no evidence of hemorrhage or necrosis. On low-power microscopy, spindle cells are apparent. At high power, the spindles are seen to be composed of fibroblastic ovarian cells with a stromal appearance. Some papillary projections are present on the cortical surface.

Radiology Discussion

On ultrasound, ovarian fibroma appears as a hypoechoic mass with attenuation of the ultrasound beam. On MR, these masses demonstrate low signal on T2 relative to the myometrium due to the predominantly fibrous composition of the mass. On CT, ovarian fibroma is a well-defined, solid mass with mild heterogeneity. Ovarian fibromas may calcify and/or exhibit cystic degeneration. They are bilateral in 3-10% of cases. Ascites is present in 10-15% of cases, especially with larger lesions.

Ovarian fibromas are the most common solid primary tumors of the ovary but are often found incidentally in the perimenopausal period. They are comprised of intersecting bundles of spindle cells. Less than 1% undergo malignant transformation to fibrosarcoma. One percent of cases are associated with Meigs syndrome, characterized by ovarian fibroma, ascites, and pleural effusion. These masses are also associated with Gorlin syndrome (basal cell nevus syndrome), characterized by multiple basal cell carcinomas, skeletal anomalies, jaw cysts, and ectopic calcifications.

The differential diagnosis includes pedunculated uterine fibroid, lymphoma, metastasis, and solid ovarian neoplasms, such as:

• Germ cell tumors: dysgerminomas, endodermal sinus (yolk sac), immature teratoma
• Stromal tumors: Sertoli-Leydig, thecoma
• Epithelial tumors: Brenner, undifferentiated epithelial tumor

Signs suggestive of malignancy in ovarian tumors include the mass being solid, especially with poor sound transmission, size greater than 10 cm, internal vascularity with high flow (RI < 0.4 or PI > 1.0), advanced age, extension of the tumor into the pelvis or surrounding viscera, ascites, and metastatic spread.

References

Dahnert W. Radiology Review Manual. Baltimore: Williams and Wilkins, 1999: 874

Lyons EA. Obstetric and Gynecologic Imaging. In: Juhl JH, Crummy AB, Kuhlman JE, ed. Essentials of Radiologic Imaging. Philadelphia: Lippincott-Raven Publishing, 1998: 763-766.

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