Role of Imaging in Differentiation Between Malignant and Benign Uterine Mass

Uterine sarcomas are rare malignant tumors arising from the mesenchymal tissues of the uterus such as the endometrial stroma, uterine muscle and connective tissue. They represent 1% of female genital tract malignancies and 3–7% of all uterine malignances. It is estimated that 0.1–0.3% of patients operated on for presumed uterine leiomyoma have a uterine sarcoma. Misclassifying a sarcoma as a benign leiomyoma may result in no or delayed treatment or surgical treatment that is inappropriate, which would be highly likely to impact negatively on prognosis. Subjective assessment of ultrasound images could help differentiate between benign and malignant myometrial tumors.
Uterine sarcomas typically appear as solid masses with inhomogeneous echogenicity, sometimes with irregular cystic areas but only very occasionally with fan-shaped shadowing. Most are moderately or very well vascularized. There are seven ultrasound features can help differentiating leiomyosarcoma from benign leiomyoma. They include irregular tumor border, loss of normal myometrium, loss of typical benign leiomyoma feature, necrosis, cystic degeneration, absent or minimal circumferential vascularity and minimal or moderate intralesional vascularity. Diagnosis of suspected uterine leiomyosarcoma requires five out of these seven features present, four gray-scale and one color Doppler ultrasound. A diagnostic algorithm including diffusion- weighted MRI criteria may help distinguish uterine sarcoma from atypical leiomyoma. An MRI diagnostic algorithm that included enlarged lymph nodes, peritoneal implants, high diffusion- weighted MRI signal greater than that in endometrium, and apparent diffusion coefficient less than or equal to 0.905 × 10−3 mm2/sec enabled identification of leiomyosarcoma.