Uterine fibroids are a common concern for many women, often leading to questions about their potential to be cancerous. It is important to understand that uterine fibroids are overwhelmingly non-cancerous growths. The occurrence of a cancerous fibroid is extremely rare, offering a reassuring outlook for those diagnosed with these benign tumors.
Understanding Uterine Fibroids
Uterine fibroids, also known as leiomyomas, are non-cancerous growths of muscle and fibrous tissue that develop within or on the uterus. These growths are common, affecting an estimated 70% to 80% of women. Many individuals experience no symptoms and are often discovered incidentally during routine pelvic examinations or imaging. When symptoms occur, they can include heavy or prolonged menstrual bleeding, pelvic pressure or pain, frequent urination, and discomfort during intercourse.
The Rare Cancerous Counterpart
A very rare uterine cancer, uterine leiomyosarcoma (LMS), can sometimes be mistaken for a fibroid. This cancer arises from the smooth muscle cells of the uterus. LMS occurs in less than 1% of cases initially presumed to be benign fibroids, with rates as low as 1 in 1,000 to 1 in 40,000. Data suggest LMS typically arises de novo, meaning it originates independently, rather than transforming from an existing benign fibroid.
How Cancerous Fibroids Are Diagnosed
Distinguishing between a benign fibroid and LMS before surgery is challenging. Imaging like ultrasound and MRI can detect masses but often cannot definitively differentiate between benign fibroids and LMS due to similar appearances. Rapid growth, sometimes associated with LMS, can also occur with benign fibroids. Diagnosis of LMS is typically made through pathological examination of tissue samples after surgical removal.
Indicators like rapid uterine mass growth, new symptoms after menopause, or unusual imaging appearance may raise suspicion. However, these signs are not exclusive to LMS and often occur with benign fibroids. Pre-operative endometrial sampling, which takes tissue from the uterine lining, can sometimes detect LMS, but its effectiveness is limited, with detection rates around 50% to 58%. This diagnostic challenge explains why LMS is often an unexpected finding after surgery for presumed fibroids.
Managing Fibroids and Cancer Concerns
Regular check-ups are important for individuals diagnosed with uterine fibroids to monitor growths and discuss symptoms. For small, asymptomatic, or mildly symptomatic fibroids, a “watchful waiting” approach is often recommended. This involves periodic evaluation without immediate treatment, as most fibroids are non-cancerous and may not cause significant problems.
Surgical removal of fibroids, known as myomectomy, or removal of the uterus, a hysterectomy, may be considered if symptoms are severe, fibroids are rapidly growing, or if there is a heightened suspicion of malignancy. Discussing any concerns or symptoms with a doctor can help determine the most appropriate management strategy and provide reassurance.