Can a Suspected Leiomyoma on CT and Ultrasound Actually Be Cancer?
Yes, a suspected leiomyoma on CT and ultrasound can be cancer, as no pelvic imaging technique—including ultrasound and CT—can reliably differentiate between benign leiomyomas and leiomyosarcomas. 1
Key Diagnostic Limitations
Ultrasound Cannot Definitively Exclude Malignancy
- Ultrasound lacks the ability to distinguish between benign leiomyomas and malignant leiomyosarcomas with certainty, despite being the first-line imaging modality for suspected fibroids 1
- Color Doppler evaluation can identify vessels within lesions but cannot definitively differentiate between benign and malignant conditions 2, 3
- Sonohysterography can characterize focal abnormalities but similarly cannot distinguish benign pathology from cancer with high certainty 2, 3
CT Has Limited Diagnostic Value
- CT pelvis has no established role in differentiating benign from malignant uterine masses 2
- Cases exist where CT suggested leiomyosarcoma but pathology revealed benign leiomyoma, demonstrating the unreliability of CT for this distinction 4, 5
Superior Imaging for Malignancy Detection
MRI Is the Gold Standard
- MRI demonstrates superior capabilities for identifying malignant uterine pathology with sensitivity and specificity up to 100% and 100% respectively for leiomyosarcomas (compared to 79% and 89% for endometrial cancer) 2, 3
- Diffusion-weighted MRI sequences specifically help differentiate leiomyosarcoma from benign leiomyoma and should be strongly considered 2, 6, 7
- MRI with gadolinium-based contrast is preferred when evaluating for potential malignancy 2
Clinical Red Flags Requiring Heightened Suspicion
Warning Signs for Malignant Transformation
- Rapid fibroid growth with tenderness in postmenopausal women should raise suspicion for leiomyosarcoma, though rare, and warrants urgent referral 6
- Giant pedunculated subserous masses with fatty degeneration can mimic malignancy on imaging 4
- Cachexia combined with a large abdominal mass may suggest malignancy but can still represent benign leiomyoma 5
Recommended Diagnostic Algorithm
When Leiomyoma Is Suspected on Initial Imaging
- Perform transvaginal and transabdominal ultrasound with Doppler as the initial evaluation 6, 1
- If ultrasound findings are suspicious, inconclusive, or the patient has concerning clinical features (postmenopausal, rapid growth, pain), proceed directly to MRI with contrast and diffusion-weighted sequences 2, 6, 7
- Do not rely on CT for distinguishing benign from malignant uterine masses 2
Specific Imaging Features to Document
- Size, location, and number of masses 1
- Presence of acoustic shadowing (typical for benign leiomyomas) 1
- Vascular patterns on Doppler (though not definitive) 2
- Any rapid interval growth on serial imaging 6
Critical Pitfalls to Avoid
- Never assume a mass is benign based solely on ultrasound or CT appearance—these modalities cannot exclude leiomyosarcoma 1
- Do not attribute new-onset tenderness to pre-existing fibroids without excluding complications or alternative diagnoses 6
- Avoid relying on imaging alone when clinical suspicion for malignancy exists—tissue diagnosis may be necessary 2, 3
- Large fibroids can displace normal ovaries and obscure visualization, potentially missing concurrent pathology 6