Uterine leiomyosarcoma is the most common uterine sarcoma, accounting for 1-3% of all uterine malignancies. Typically occurs in women over 50 (mean age 50-55). It is a high-grade malignant tumor originating from smooth muscle cells of the myometrium. Presents with rapid growth, postmenopausal bleeding, and pelvic mass. Preoperative differentiation from benign leiomyoma (fibroid) is challenging — this is the most important clinical and imaging problem. The diagnostic triad consists of coagulative necrosis, high mitotic activity (≥10 mitoses/10 HPF), and marked cytological atypia. MRI, particularly T2 heterogeneity, coagulative necrosis (T1 hyperintensity), and DWI diffusion restriction, helps differentiate from leiomyoma. Prognosis is poor; 5-year survival ranges from 25-50%.
Age Range
40-70
Peak Age
55
Gender
Female predominant
Prevalence
Rare
Uterine leiomyosarcoma develops de novo from smooth muscle cells of the myometrium — importantly, malignant transformation from existing benign leiomyomas is extremely rare (<0.1%). TP53 mutation, RB1 loss, PTEN inactivation, and complex genomic rearrangements play a role in tumor pathogenesis. p53 and p16 are overexpressed immunohistochemically. High cellular density, coagulative (ischemic) necrosis, and increased mitotic activity are characteristic. Coagulative necrosis develops when the tumor's rapid growth outpaces blood supply — these necrosis areas appear as T1 hyperintensity (proteinaceous/hemorrhagic content) on MRI and differ from hyaline degeneration in benign leiomyoma. Diffusion restriction on DWI reflects high cellularity — the dense, irregularly packed malignant cells of leiomyosarcoma markedly restrict water diffusion. T2 heterogeneity results from the coexistence of necrosis, hemorrhage, and varying cellular density areas — different from the typical homogeneous T2 hypointensity of benign leiomyomas. On contrast-enhanced MRI, peripheral enhancement and central necrosis (peripheral enhancing rim) reflect aggressive growth.
The combination of T2 heterogeneous signal + T1 hyperintense areas (coagulative necrosis) + DWI diffusion restriction triad on MRI is the strongest diagnostic combination for leiomyosarcoma. This triad is not seen in benign leiomyoma (including degeneration) and has the highest specificity in leiomyoma-leiomyosarcoma differentiation.
Leiomyosarcoma shows markedly heterogeneous signal on T2-weighted MRI — this is the most important distinguishing finding. High cellular areas show intermediate T2 signal, necrotic areas show high T2 signal, hemorrhagic areas show variable signal. Homogeneous T2 hypointensity (typical appearance of benign leiomyoma) is NOT SEEN in leiomyosarcoma. The mass is usually >5 cm and has irregular margins. Appears as an intramural mass arising from the myometrium — expands the myometrium, not the endometrial cavity. May show subserosal or intracavitary extension.
Report Sentence
A markedly heterogeneous signal mass measuring [X] cm is identified in the myometrium on T2-weighted sequences without homogeneous T2 hypointensity; leiomyosarcoma should be considered in the differential diagnosis.
T1-weighted MRI shows T1-hyperintense areas within leiomyosarcoma — these areas are consistent with coagulative necrosis and/or hemorrhage. Coagulative necrosis is one of the most important pathological criteria of leiomyosarcoma and differs from hyaline (acellular) degeneration in benign leiomyoma. Hyaline degeneration is T1-hypointense with variable T2 signal; coagulative necrosis appears T1-hyperintense (due to proteinaceous/hemorrhagic content). This distinction has critical diagnostic importance.
Report Sentence
T1-hyperintense areas are identified within the myometrial mass on T1-weighted sequences, consistent with coagulative necrosis/hemorrhage; this finding is a strong indicator favoring leiomyosarcoma.
Leiomyosarcoma shows markedly bright signal at high b-values on DWI with low signal on ADC map. ADC values are generally <1.0 x 10-3 mm2/s — in benign leiomyomas, ADC values are generally >1.2 x 10-3 mm2/s. The entire mass shows diffuse or heterogeneous restriction. DWI improves diagnostic accuracy in addition to T2 and T1 findings for leiomyoma-leiomyosarcoma differentiation. A gray zone exists with ADC values between 0.9-1.1 x 10-3 mm2/s — in this range, differentiation between cellular leiomyoma and low-grade leiomyosarcoma may be difficult.
Report Sentence
Marked diffusion restriction is identified in the myometrial mass on DWI with low ADC values (<1.0 x 10-3 mm2/s), indicating high cellularity and interpreted in favor of leiomyosarcoma.
Contrast-enhanced MRI shows peripheral enhancement and central necrosis (non-enhancing area) in leiomyosarcoma. Peripheral rim enhancement reflects viable, vascular tissue at the periphery and necrotic tissue at the center of the tumor. The enhancement pattern is heterogeneous — different from the homogeneous enhancement of benign leiomyoma. Less enhancement than myometrium is seen in the delayed phase. Irregular margins and blurred boundary with surrounding myometrium are additional findings favoring malignancy.
Report Sentence
Peripheral enhancement and central necrosis (non-enhancing area) are identified in the myometrial mass on contrast-enhanced MRI, reflecting an aggressive growth pattern consistent with leiomyosarcoma.
Contrast-enhanced CT shows leiomyosarcoma as a large (usually >5 cm), heterogeneously enhancing myometrial mass. Central hypodense areas reflect necrosis. Calcification is less common than in benign leiomyomas. CT evaluates pelvic and para-aortic lymph nodes, peritoneal spread, and distant metastases (lung most common). Local invasion (bladder, rectum, pelvic sidewall) may be detected. CT is limited compared to MRI for leiomyoma-leiomyosarcoma differentiation but valuable for metastasis screening.
Report Sentence
A heterogeneous mass measuring [X] cm with central necrotic area is identified in the myometrium on contrast-enhanced CT; leiomyosarcoma should be considered in the differential diagnosis. Pelvic MRI is recommended for characterization.
Transvaginal/transabdominal US shows leiomyosarcoma as a large, heterogeneous echogenicity myometrial mass. Irregular margins, central hypoechoic necrosis areas, and increased vascular flow (Doppler) may be seen. Cannot be reliably differentiated from benign leiomyomas by US — rapid growth history and new symptoms increase suspicion. US is used for initial assessment but MRI is mandatory when leiomyosarcoma is suspected.
Report Sentence
A heterogeneous mass measuring [X] cm is identified in the myometrium on US; considering the history of rapid growth, leiomyosarcoma should be excluded, pelvic MRI characterization is recommended.
Criteria
Most common subtype (75-80%). Spindle-shaped (fusiform) smooth muscle cells, high mitotic activity (≥10 mitoses/10 HPF), coagulative necrosis, marked cytological atypia. Desmin and h-caldesmon positive (smooth muscle markers).
Distinct Features
Typical MRI findings (T2 heterogeneity, T1 hyperintensity, DWI restriction), usually >5 cm, rapid growth, prognosis correlates with stage and grade.
Criteria
Rare variant (5-10%). Round/polygonal epithelioid cells. Desmin weakly positive, keratin negative. Lower mitotic threshold (≥5 mitoses/10 HPF sufficient).
Distinct Features
Epithelioid morphology, less aggressive course, may appear more homogeneous on T2, difficult to differentiate from benign epithelioid leiomyoma.
Criteria
Rare variant (5%). Rich myxoid stroma. Low cellularity but marked atypia. May appear similar to benign myxoid leiomyoma. Very bright signal on T2 (myxoid matrix high water content).
Distinct Features
Very bright signal on T2 (myxoid matrix), ADC values may be high (low cellularity), DWI can be misleading — coagulative necrosis and atypia critical for diagnosis, poor prognosis.
Distinguishing Feature
Benign leiomyoma is homogeneously hypointense on T2, shows no T1 hyperintense coagulative necrosis, no marked restriction on DWI (ADC >1.2), well-defined, slow growing.
Distinguishing Feature
STUMP (smooth muscle tumor of uncertain malignant potential) is in the gray zone between leiomyoma and leiomyosarcoma — usually does not meet all MRI criteria for leiomyosarcoma, may lack coagulative necrosis, mitotic activity is below threshold.
Distinguishing Feature
Endometrial stromal sarcoma shows worm-like extension from endometrial cavity into myometrium and intravascular extension is pathognomonic — leiomyosarcoma is an intramural mass without intravascular extension.
Distinguishing Feature
Type II endometrial carcinoma originates from the endometrial cavity (not intramural), shows JZ disruption, is an epithelial tumor (not sarcoma), peritoneal spread is more common.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralPreoperative diagnosis is challenging — most cases are operated with a presumed diagnosis of leiomyoma and leiomyosarcoma is diagnosed on pathology. If the triad of T2 heterogeneity + T1 hyperintensity + DWI restriction is present on MRI, preoperative suspicion should increase and the patient should be referred to a gynecologic oncology center. Standard treatment is total hysterectomy + bilateral salpingo-oophorectomy — morcellation is absolutely contraindicated (risk of peritoneal dissemination). The role of lymph node dissection is debated. Adjuvant chemotherapy (doxorubicin/ifosfamide or gemcitabine/docetaxel) is applied in advanced and high-risk cases. The role of radiotherapy is limited. Recurrence risk is high (50-70%) and lung metastasis is most common. Targeted therapies (pazopanib, trabectedin) are second-line options.
Leiomyosarcoma is an aggressive tumor with poor prognosis. It spreads hematogenously (lungs most common). Surgery (total hysterectomy) is the primary treatment. Response to chemotherapy is limited. 5-year survival is 15-25%. A rapidly growing 'leiomyoma' in the postmenopausal period must be evaluated for sarcoma.