Uterine Leiomyosarcoma

Uterine leiomyosarcoma is a rare and aggressive uterine malignancy usually in postmenopausal women, presenting as a large heterogeneously enhancing mass containing atypical spindle cells, significant nuclear pleomorphism, high mitotic rate with areas of necrosis and haemorrhage.

Description

Uterine leiomyosarcoma is a rare and aggressive subtype of uterine sarcoma that originates from the smooth muscle cells in the myometrium of the uterus. This highly malignant variant is a part of the broader family of soft tissue sarcomas. It is the most common type of uterine sarcoma, yet it still constitutes only about 1% of all uterine malignancies.

Pathogenesis

The precise pathogenesis of uterine leiomyosarcoma is yet to be fully elucidated. However, it is known that this tumour arises from the uncontrolled proliferation of smooth muscle cells in the myometrium. Some instances of uterine leiomyosarcomas are associated with genetic disorders such as hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome, but most cases seem to occur sporadically.

Epidemiology, Risk Factors & Associations

• Uterine leiomyosarcomas account for roughly 1% of all uterine malignancies and about 30% of uterine sarcomas.
• They predominantly occur in postmenopausal women, with the median age at diagnosis being approximately 55 years.
• Black women have a disproportionately higher incidence of uterine leiomyosarcomas than women of other ethnicities.
• Prolonged use of tamoxifen and pelvic irradiation have been identified as potential risk factors.
• The association with hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome is also notable.

Clinical Features

• The most common presenting symptoms include abnormal uterine bleeding, pelvic pain, and an enlarged uterus. Occasionally, the tumour may be detected incidentally during surgery for presumed benign fibroids.
• Rapidly enlarging uterine fibroids in postmenopausal women should raise suspicion for uterine leiomyosarcoma.

Complications

• The most feared complication of uterine leiomyosarcoma is metastasis, which typically involves the lungs, liver, and peritoneum.
• The aggressive local spread can result in invasion into neighbouring organs, leading to urinary or bowel complications.

Pathological Features

Histopathology

• Macroscopic: Uterine leiomyosarcomas typically appear as large, fleshy, haemorrhagic masses that often fill the uterine cavity and may extend into the cervix.
• Microscopic: Histological features include interlacing bundles of atypical spindle cells demonstrating significant nuclear pleomorphism, hyperchromasia, and increased mitotic activity. Areas of coagulative tumour necrosis and haemorrhage are commonly seen.

Radiological Features

General Features

• Uterine leiomyosarcomas generally appear as large, well-defined, heterogeneously enhancing masses on imaging studies.
• Central necrosis and haemorrhage, common features of this tumour, result in a heterogeneous imaging appearance.

Ultrasound

• On ultrasound, leiomyosarcomas may appear as heterogeneous masses with areas of echogenicity corresponding to necrosis or haemorrhage.

CT

• Non-contrast: On non-contrast CT, uterine leiomyosarcomas appear as large, well-defined, soft tissue masses.
• Contrast-enhanced: On contrast-enhanced CT, these tumours show heterogeneous enhancement with areas of hypoattenuation corresponding to necrosis or haemorrhage.

MRI

• T1WI: The tumour generally appears isointense or slightly hyperintense compared to the myometrium.
• T2WI: On T2-weighted images, the tumour is typically heterogeneous and hyperintense, with areas of hypointensity corresponding to haemorrhage or necrosis.
• T1 C+: After gadolinium contrast administration, the tumour enhances heterogeneously.

Grading and Staging

The grading of uterine leiomyosarcomas is based on histological features such as cellularity, atypia, and mitotic count. The staging is performed according to the FIGO (International Federation of Gynecology and Obstetrics) system for uterine sarcomas.

Diagnosis

The diagnosis of uterine leiomyosarcoma is challenging due to its overlapping features with benign leiomyomas. It requires a combination of clinical suspicion, imaging findings, and histopathological examination. Definitive diagnosis is often made post-operatively on histopathological examination of the surgical specimen.

Differential Diagnosis

• Leiomyoma: Benign smooth muscle tumour of the uterus, typically displays less enhancement and lacks necrotic or haemorrhagic components on imaging.
• Endometrial carcinoma: Typically arises from the endometrium with an entirely different clinical and imaging presentation.
• Other uterine sarcomas: Such as endometrial stromal sarcoma, may also need to be considered.

Management

The management of uterine leiomyosarcoma usually involves total hysterectomy with bilateral salpingo-oophorectomy. The role of lymphadenectomy remains controversial. Adjuvant therapy with chemotherapy and/or radiation therapy may be considered based on the stage of the disease and the patient’s overall health status. The management should ideally be conducted by a multidisciplinary team of specialists, including gynaecological oncologists, radiologists, and pathologists.