Uterine sarcomas are rare malignant tumors arising from the mesenchymal tissues of the uterus, i.e. the endometrial stroma, uterine muscle and connective tissue. They represent 1% of female genital tract malignancies and 3-7% of all uterine malignances.

Abstract: Uterine sarcomas are rare malignant tumors arising from the mesenchymal tissues of the uterus, i.e. the endometrial stroma, uterine muscle and connective tissue.  They represent 1% of female genital tract malignancies and 3-7% of all uterine malignances.

In a retrospective analysis of 116 leiomyosarocmas, 48 endometrial stroma sarcomas and 31 undiffrenentiated sarcomas the following results were found: Most sarcomas were solid masses (>80% solid tissue) (79.5%) and most manifested inhomogeneous echogenicity of the solid tissue (77.4%). Cystic areas were described in half of tumors and most cyst cavities had irregular walls (77.0%). Internal shadowing was observed in 21.9% sarcomas and fan shaped shadowing in 2.1%. Moderate or rich vascularization was found on color Doppler in 67.9% of cases. Visible normal myometrium was reported in 76.4% cases, and 80% of lesions were solitary.

Uterine sarcomas typically appear as solid masses with inhomogeneous echogenicity, sometimes with irregular cystic areas but rarely with fan shaped shadowing. Most are moderately or very well vascularized.

Key words: Uterine sarcomas, leiomyosarcoma; endometrial stromal sarcoma; undifferentiated endometrial sarcomas.

Authors: Manuela Ludovisi, MD1; Antonia Carla Testa, MD1

  1. Dipartimento Scienze della Salute della Donna e del Bambino, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy.

Reviewers: Lil Valentin, Elisabeth Epstein

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Uterine sarcomas are rare malignant tumors arising from the mesenchymal tissues of the uterus, i.e. the endometrial stroma, uterine muscle and connective tissue.  They represent 1% of female genital tract malignancies and 3-7% of all uterine malignances1. Population-based estimates of uterine sarcoma incidence range from 1.55 to 1.95 per 100,000 women per year. It is estimated that ≤0.1% of patients operated on for presumed uterine leiomyoma have a uterine sarcoma2. According to the 2011 WHO classification, uterine sarcomas are classified as leiomyosarcomas, endometrial stromal sarcoma or undifferentiated endometrial sarcoma3,4. The median age of women with leiomyosarcomas was 50-56 years at diagnosis5, endometrial stromal sarcomas 40-55 years and undifferentiated stromal sarcomas 55-60 years4.


Age adjusted incidence of leiomyosarcoma was twice as high in black compared to white women5. Other risk factors were advanced age and postmenopausal status. Associations between endometrial stromal sarcoma and exposure to tamoxifen, unop­posed estrogen5 and polycystic ovary syndrome have also been reported. Endometrial stromal sarcoma is more common in women with past history of pelvic radiation5.


Leiomyosarcomas average 6-9 cm in diameter and the cut surface is typically soft, bulging, fleshy, necrotic and hemorrhagic with irregular margins6. Infiltrative growth into the myometrium is often noted grossly (or under the microscope), but some leiomyosarcomas may be relatively well circumscribed. About two-thirds are intramural, one-fifth submucosal and one tenth subserosal6. They are often single masses (50-75% of cases)4 If a leiomyosasrcoma is associated with leiomyomas, the sarcoma is usually the largest mass6. Leiomyosarcomas tend to be larger and softer than leiomyomas4. Endometrial stromal sarcomas have an irregular nodular growth involving the endometrium, myometrium, or both. Size is variable but most range from 5 to 10 cm. They typically have a yellow to tan fleshy cut surface with hemorrhage and necrosis occasionally seen6.

Undifferentiated endometrial sarcomas grow as soft polypoid tumors that bulge into the endometrial cavity and invade the underlying myometrium. Hemorrhage and necrosis are frequently present6.


Histopathological diagnosis of uterine sarcomas has always been a challenge, because many benign variants of smooth muscle tumors, e.g. mitotically active leiomyomas, apoplepletic leiomyomas and leiomyomas with bizarre nuclei, can simulate leiomyosarcormas. Diagnosis of endometrial stromal is also difficult which is reflected if frequent changes in their classification. The histopathologic diagnosis of uterine leiomyosarcoma is based upon mitotic count exceeding 10 mitotic figures per 10 high-power-fields (MF/10 HPF), cellular atypia, and the presence of coagulative necrosis7.  Leiomyosarcomas are composed of fascicles of spindle cells with abundant eosinophilic cytoplasm7 Cellular pleomorphism can be marked in poorly differentiated neoplasms. The mitotic index is usually high6. Tumor cell necrosis occurs in one third and is characterized by an abrupt transition from viable to not viable tissue. Both cytological atypia and mitotic activity should usually be present to diagnose leiomyosarcomas, because of the difficulty in reliably distinguishing between necrosis due to infarction and tumor cell necrosis6. The term endometrial stromal sarcoma is applied to neoplasms composed of cells that resemble endometrial stromal cells of the proliferative endometrium6. Endometrial stromal sarcomas are low grade tumors with cells of relatively uniform size and shape. They typically show < 3 MF/10 HPF, but there can also be greater mitotic activity1 Proliferation of small vessels and arterioles resembling endometrial spiral arterioles is a characteristic finding. Cluster of differentiation 10 (CD10) - a metalloproteinase - is the most specific biomarker of endometrial stromal sarcoma. 

In undifferentiated endometrial sarcomas, tumor cell necrosis is generally present and can be extensive. Mitotic activity is variable but there are usually > 10 MF/10 HPF1. These tumors should be diagnosed only after extensive sampling has excluded smooth muscle or skeletal muscle differentiation or small foci of carcinoma, because findings of these would result in a diagnosis of carcinosarcoma.

Clinical symptoms

Leiomyosarcomas often present with symptoms of abnormal uterine bleeding (56%) either in the pre- or post-menopausal period, a palpable pelvic mass (54%), or abdominal pain (22%)1. Signs and symptoms resemble those of benign leiomyomas, and preoperative distinction on the basis of clinical information between the two may be difficult. Malignancy should be suspected in case of tumor growth in menopausal women who are not on hormonal replacement therapy8 Occasionally, the presenting symptoms are explained by tumor rupture (hemoperitoneum), extrauterine growth (one-third to one-half of cases), or metastases6. Patients with endometrial stromal sarcomas often present with abnormal uterine bleeding and/or pelvic pain, but as many as 25% are asymptomatic9.

Ultrasound characteristics

Recently Ludovisi et al10 retrospectively collected the preoperative ultrasound reports of 195 patients with a histological diagnosis of uterine sarcomas from 13 ultrasound centers: 116 leiomyosarcomas, 48 endometrial stromal sarcomas and 31 undifferentiated endometrial sarcomas. Median age of the patients was 56 (range, 26-86) years and most patients were postmenopausal (111/195, 56.9%).

Median largest tumor diameter was 91 (range 7-321) mm. According to the assessment by the original examiners (first step of analysis), all but one sarcoma with reliable information on tumor type (n = 172) contained solid components and the vast majority were solid tumors (155/172, 90%). Most sarcomas manifested inhomogeneous echogenicity of the solid tissue (151/195, 77.4%), cystic areas were described in 87/195 (44.6%), and most of the cystic areas had irregular walls (67/87, 77.0%). Internal shadows were found in 42/192 (21.5%) of cases, while fan shaped shadowing was rare (4/192, 2.1%).

Tumor borders were found to be irregular in 103/195 (52.8%) cases. Moderate or rich vascularization was observed in 127/187 (67.9%) tumors with reliable color Doppler information.

Leiomyosarcomas were larger than endometrial stromal sarcomas and undifferentiated endometrial sarcomas (median largest diameter 106 mm vs 68 vs 70). Endometrial stromal sarcomas manifested the highest percentage of visible normal endometrium (44/48, 91.7%) and regular tumor borders (29/48, 60.4%) and were less vascularized than the other sarcomas (score 1-2 in 20 of 47 tumors with reliable color Doppler information, 42.5%). Undifferentiated endometrial sarcomas manifested the highest percentage of absent shadowing (27/31, 87.1%), irregular tumor borders (23/31, 74.2%), and hemorrhagic or ground glass echogenicity of cyst fluid (6/15, 40%).


Leiomyosarcomas are very aggressive tumors with poor prognosis6. The treatment includes total abdominal hysterectomy and debulking of tumor outside the uterus. Oophorectomy is generally recommended, but it might not be necessary in patients of reproductive age with early stage disease. Lymph node dissection is controversial, but if there are no signs of metastatic lymph nodes, lymph node dissection can be spared11. The role of adjuvant radiation therapy for patients with Stage I/II leiomyosarcoma is highly controversial, because it does not seem to affect either progression or survival12. Occasionally, estrogen-receptor positive tumors will respond to hormonal treatment, for example progestin, aromatase inhibitor, Gonadotrophin Releasing Hormone (GnRH) analogues or GnRH analogues plus megestrol acetate.

Endometrial stromal sarcomas are indolent tumors with a favorable prognosis. Stage is the most important prognostic factor. The 5-year disease specific survival for stage I and II tumors is 90% compared to 50% for stage III and IV13. Surgical treatment of endometrial stromal sarcomas is hysterectomy and bilateral salpingo-oophorectomy14. However, in young patients affected by early stage endometrial stromal sarcoma who wish to preserve reproductive function, fertility sparing surgery (hysteroscopic removal of the lesion and sparing of uterus and ovaries) is an option. Endometrial stromal sarcomas are usually hormone receptor‑positive, and progestins and aromatase inhibitors are used as adjuvant treatment for this disease.

Undifferentiated endometrial sarcomas have very poor prognosis, and most patients die of the disease within 2 years from diagnosis6. Treatment is primarily surgical with or without adjuvant radiotherapy or chemotherapy.


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This article should be cited as: Ludovisi M., Testa A.C: Uterine Sarcomas, Visual Encyclopedia of Ultrasound in Obstetrics and Gynecology, www.isuog.org, February 2020.