Endometrial Stromal Sarcoma

Bang Huu Huynh, MD - Case Coordinator
Hope Elizabeth Peters, MD - Radiology Discussion
Jian Shen, MD, PhD - Pathology Discussion
Donald N Di Salvo, MD - Attending Radiologist
Steven E Seltzer, MD - Attending Radiologist

May 12, 2003

Presentation

Imaging Findings

MR images through the pelvis show a mass arising from the dome of the uterus. The signal is hypointense to muscle, but higher than water; it is not a typical signal level for fibroid. Stranding is apparent. The myometrium is not visible. The mass enhances strongly with contrast, and the stranding (possibly representing septations) is more obvious. The lesion appears to be solid.

Differential Diagnosis

Diagnosis

Discussion

A hysterectomy was performed. The gross specimen demonstrates a large (14.5 cm) polypoid mass occupying the endometrial cavity. Microscopy shows trabecular infiltration of tumor cells in the myometrium; lymphatic invasion is also apparent. In fact, the tumor extends to within 0.1 cm of the serosal surface. Immunohistochemistry studies show that tumor cells are positive for CD-10 and negative for desmin and caldesmon, leading to the diagnosis of endometrial stromal sarcoma. This is a low-grade tumor that does not involve the ovaries or fallopian tubes. Five left and two right external iliac lymph nodes were examined and also found to be free of tumor.

Radiology Discussion:

Uterine sarcomas represent 2-5% of all uterine malignancies. There are three types: carcinosarcoma (also known as mixed mullerian tumor) is the most common, leiomyosarcoma is next, and endometrial stromal sarcoma (ESS) is the least common (<10% of uterine sarcomas). Endometrial stromal sarcomas are composed of cells that are identical to or closely resemble normal proliferative-phase endometrial stromal cells. These tumors may arise from the endometrium but can also be seen in the setting of adenomyosis or endometriosis.

Endometrial stromal sarcoma typically occurs in women between the ages of 42 and 59 years. Symptoms include abnormal uterine bleeding and pain. Risk factors are fairly nonspecific and include prior pelvic radiation therapy, age, and race (slightly higher incidence among blacks). There may also be hormonal factors, though this is not well understood. The differential diagnosis for ESS includes leiomyoma with cystic degeneration, leiomyosarcoma, and endometrial carcinoma. The subtle differences between these entities are best demonstrated with MRI.

On MR, endometrial stromal sarcomas appear as large tumors in the endometrial cavity and/or myometrium. The signal is typically high on T1-weighted images and heterogeneously high on T2-weighted images. The tumor margins are typically irregular, often with marginal nodular lesions. Intramyometrial worm-like nodular extensions may be visible. Hemorrhage and necrosis are common. Most ESS show greater enhancement than normal myometrium. Overall, ESS are difficult to differentiate from leiomyomas with cystic degeneration, leiomyosarcomas, and endometrial carcinomas.

There are, however, several imaging features that differentiate ESS from those other tumors. Endometrial carcinomas typically do not display irregular marginal lesions, marginal nodules or intramyometrial nodules. The avid enhancement pattern of ESS (relative to the myometrium) is also not typical for endometrial carcinomas. Leiomyomas and leiomyosarcomas generally do not have the high T2 signal that is characteristic of ESS. In addition, these tumors display a different pattern of enhancement; markedly increased signal after contrast is unusual. Finally, leiomyomas typically do not have irregular margins with small nodules (though these features may be seen in leiomyosarcomas).

References

Ueda M, et al. Uterine endometrial stromal sarcoma located in uterine myometrium: MRI appearance. Eur Radiol. (2000)10, 780-782.

Gandolfo, et al. Endometrial stromal sarcoma of the uterus: MR and US findings, Eur Radiol. (2000) 10, 776-779.

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