There are three major ways doctors describe fibroid sizes. Family practice doctors typically describe fibroid sizes in terms of fruits. Gynecologists with experience in fibroid management may describe fibroids by the equivalence of gestational age. Meanwhile, a radiologist will describe a fibroid in terms of diameter in millimeters or centimeters.
For example, a woman visiting her family physician is found to have a fibroid may describe it as being the size of a mango, strawberry, or watermelon. That same fibroid from a gynecologist’s perspective would be described as 10 weeks, 25 weeks, or 40 weeks gestational age. After imaging, a radiologist may describe the fibroid by its dimensions.
A quick conversion chart for fibroid sizes can be found at the end of this post.
All fibroids are not equal. A 2-cm submucosal fibroid, which is in the uterine cavity occupying majority of the space, will have far more impact on a patient’s life than a 10-cm pedunculated subserosal fibroid. A submucosal fibroid is the least common of the different types of fibroids, however, it is primarily responsible for heavy or abnormal bleeding and subfertility.
So, what’s the correct way to describe fibroids? In this post, we argue that the most accurate way to describe a fibroid is in terms of its weight in grams. Heavier fibroids will have worse symptoms leading to a lower quality of life for the patient. Here, we will briefly review what fibroids are and then delve into measuring the volume and weight in grams of fibroids for both professionals and non-professionals.
Uterine leiomyomas or fibroids, are the most common benign neoplasms occurring in women of reproductive age. Some studies have estimated that up to 70% to 80% of all women will develop at least one fibroid during their lifetime. Although fibroids are benign, they can have detrimental effects on quality of life.
Common symptoms of uterine fibroids include:
- Abnormally heavy or prolonged menstrual bleeding
- Heavy bleeding between periods
- Pain or pressure in pelvic region
- Bladder problems
- Painful intercourse
- Abnormal weight gain
- Pain in lower back
For a gynecology professional, it can be important to obtain the accurate size or weight of the fibroids to help direct management. This article will help alleviate the anxiety or stress that comes with complex calculations and may help simplify the process.
The diagnosis of uterine fibroids has typically been made by using ultrasound due to its low cost, simplicity, and noninvasiveness. It has been estimated that transvaginal ultrasounds have a reliability of 98% to 100% when it comes to diagnosing uterine fibroids.
With the advent of 3D ultrasound devices, volume calculations have become significantly more precise, especially with the aid of VOCAL (Volume Calculation or Virtual Organ Computer-Aided analysis). However, in the hands of an experienced clinician, a 2D-ultrasound device can also be used to with high precision. When ultrasound evaluation is inadequate, MRI should be used.
Conversions and Calculations
2D ultrasounds are one of the most commonly used devices in the gynecologic setting. To calculate the volume of an ovoid body, 3 distances must be measured. D1 is the distance between two opposite poles in the longest transverse fibroid section. Next, the width of the fibroid must be calculated going from anterior-posterior diameter to determine D2. Lastly, D3 is the transverse diameter on the vertical length of the anterior-posterior diameter.
Once the diameters have been established, simply plug into the following equation:
Similarly, D1, D2, D3 can be substituted with L (craniocaudal length), W (transverse width), AP (anterior-posterior diameter). The equation would be the same.
Measuring the weight of fibroids in grams
Density = mass/volume
Therefore, density has the units grams per cubic centimeter (g/cm3)
Fat density: 0.9094 g/cm3
Muscle density: 1.0599 g/cm3
Myomas land approximately in between the density of fat and muscle. As such, we will assume a rough estimation of 1.0 g/cm3 for fibroids. To calculate the weight of an individual fibroid, the volume must first be ascertained by the above equations and then plugged in the following equation for weight (W):
The conversion should result in weight (W) in grams.
A fibroid is found to have the dimensions 2.5 cm x 3.0 cm x 1.0 cm.
Those dimensions inserted into the equation for volume:
Then, insert volume (V) into the equation for weight (W):
Therefore, the weight of a fibroid with the dimensions 2.5 cm x 3.0 cm x 1.0 is 3.9 grams.
Major weakness of ultrasound
It is worthy to note—an ultrasound evaluation of fibroids cannot differentiate between a benign fibroid and a malignant leiomyosarcoma. One study found that nearly 1/450 women that underwent surgery for fibroids were found to have sarcomas after histopathology. Therefore, it should always be considered when evaluating fibroids.
For women suffering from fibroids
If you think uterine fibroids are an issue for you, Dr. Lyndon Taylor and his team are the fibroid experts you’ve been searching for. If you’re ready to live a better and healthier life, call 708-848-9440 for more information.
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Fibroid size conversion chart for reference:
 Bulun SE. Uterine Fibroids. New England Journal of Medicine. 2013;369:1344-55. DOI: 10.1056/NEJMra1209993.
 Zivkovic N, Zivkovic K, Despot A, Paic J, Zelic A. Meausre the volume of uterine fibroids using 2- and 3-dimentional ultrasound and comparison with histopathology. Act Clin Croat. 2012;51:579-589.
 Moshesh M, Peddada SD, Cooper T, Baird D. Intraobserver variability in fibroid size measurements: estimated effects on assessing fibroid growth. J Ultrasound Med. 2014;33(7):1217-24. DOI:10.7863/ultra.33.7.1217.
 "Density and hydration of fresh and fixed human skeletal muscle", Samuel R. Ward, Richard L. LieberCorresponding Author Information, Accepted 6 October 2004. published online 04 January 2005.http://www.jbiomech.com/article/S0021-9290%2804%2900507-X/abstract
 "Accurate and Easy Bodyfat Determination", http://mb-soft.com/public2/bodyfat.html, Oct 2010.
 Wilde S, Scott-Barrett S. Radiological appearances of uterine fibroids. Indian J Radiol Imaging. 2009;19(3):222-231.