The three most common histologic variants of uterine sarcoma are endometrial stromal sarcoma (ESS), leiomyosarcoma, and carcinosarcoma (malignant mixed m¨ullerian tumor, or MMMT) of both homologous and heterologous type (406) (Table 35.15). Variations in the relative incidences of uterine sarcomas occur in published series, probably related to the strictness of criteria used to classify smooth muscle and endometrial stromal tumors as sarcomas. Leiomyosarcoma and carcinosarcoma each constitute approximately 40% of tumors, with carcinosarcoma predominating in more recent reports, followed by ESS (15%) and other sarcomas (5%).
Staging Staging of uterine sarcomas is based on the FIGO system (Table 35.16).
Stromal tumors occur primarily in perimenopausal women between ages 45 and 50 years; about one-third occurs in postmenopausal women. There is no relationship to parity, associated diseases, or prior pelvic radiotherapy. These tumors are rare in African-American women. The most frequent symptom is abnormal uterine bleeding; abdominal pain and pressure caused by an enlarging pelvic mass occur less often, and some patients do not have symptoms. Pelvic examination usually reveals regular or irregular uterine enlargement, sometimes associated with rubbery parametrial induration. The diagnosis may be determined by endometrial biopsy, but the usual preoperative diagnosis is uterine leiomyoma. At surgery, the diagnosis is suggested by the presence of an enlarged uterus filled with soft, gray-white to yellow necrotic and hemorrhagic tumors with bulging surfaces associated with wormlike elastic extensions into the pelvic veins.
Endometrial stromal tumors are composed purely of cells resembling normal endometrial stroma. They are divided into three types on the basis of mitotic activity, vascular invasion, and observed differences in prognosis: (i) endometrial stromal nodule, (ii) endometrial stromal sarcoma, and (iii) high-grade or undifferentiated sarcoma.
Endometrial stromal nodule is an expansive, noninfiltrating, solitary lesion confined to the uterus with pushing margins, no lymphatic or vascular invasion, and usually less than 5 mitotic figures per 10 high-power microscopic fields (5 MF/10 HPF). These tumors should be considered benign because there are no recurrences or tumor-associated deaths reported after surgery (406,407).
Table 35.15 Classifications of Uterine Sarcomas
I. Pure nonepithelial tumors
A. Homologous 1. Endometrial stromal tumors a.
b.
2. Smooth muscle tumors a.
b.
1.
2.
c. Benign metastasizing tumors 1.
2.
3.
B. Heterologous 1.
2.
3.
4.
II.
A.
1.
2.
B. Adenosarcoma
Modified from Clement P, Scully RE. Pathology of uterine sarcomas. In: Coppleson M, ed. Gynecologic oncology: principles and practice. New York: Churchill-Livingston, 1981, with permission.