Type 1 -less than 50% of the fibroid diameter within the myometrium
Type 2 -50% or more of the fibroid diameter within the myometrium
Type 3 -abut the endometrium without any intracavitary component
Type 4 -intramural and entirely within the myometrium, without extension to either the endometrial surface or to the serosa
Type 7 -subserosal attached to the serosa by a stalk
Type 8 -no involvement of the myometrium; includes cervical lesions, those in the round or broad ligaments without direct attachment to the uterus, and
Transmural fibroids are categorized by their relationship to both the endometrial and the serosal surfaces, with the endometrial relationship noted first, e.g., type 2–3 (Table 15.1; Fig 15.2) (60).
Imaging For symptomatic women, consideration of medical therapy, noninvasive procedures, or surgery often depends on an accurate assessment of the size, number, and position of fibroids. Transvaginal sonography (TVS), saline-infusion sonography (SIS), hysteroscopy, and MRI were all performed on 106 women scheduled for hysterectomy and the findings were compared to pathologic examination (59). Submucous fibroids were best identified with MRI (100% sensitivity, 91% specificity). Identification was about equal with transvaginal sonography (sensitivity 83%, specificity 90%), saline-infusion sonography (sensitivity 90%, specificity 89%), and hysteroscopy (sensitivity 82%, specificity 87%). MRI is not technique dependent and has low interobserver variability for diagnosis of submucous fibroids, intramural fibroids, and adenomyosis when compared with TVS, SIS, and hysteroscopy (61,62).
Table 15.1 FIGO Leiomyoma Classification System
The presence of adenomyosis is associated with junctional zone thickness of more than 15 mm (or 12 mm in a nonuniform junctional zone). Focal, not well-demarcated, and high or low intensity areas in the myometrium correlate with adenomyosis (63).
MRI allows evaluation of the number, size, and position of submucous, intramural, and subserosal fibroids and can evaluate their proximity to the bladder, rectum, and endometrial cavity. MRI helps define what can be expected at surgery and might help the surgeon avoid missing fibroids during surgery (64). For women who wish to preserve fertility, MRI to document location and position relative to the endomyometrium may be helpful prior to hysteroscopic, laparoscopic, or abdominal myomectomy.
Figure 15.2 FIGO Leiomyoma Classification System.
Imaging of Uterine Sarcomas
Sonography is the most readily available and least costly imaging technique to differentiate fibroids from other pelvic pathology and is reasonably reliable for evaluation of uterine volume less than 375 cc and containing four or fewer fibroids (61). Sonographic appearance of fibroids can be variable, but often they appear as symmetrical, well-defined, hypoechoic and heterogenous masses. Areas of calcification or hemorrhage may appear hyperechoic, while cystic degeneration may appear anechoic. SIS utilizes saline inserted into the uterine cavity to provide contrast and better defines submucous fibroids (61).