Imaging description

At ultrasound, it is usually straightforward to determine that a mass adjacent to the uterus is an exophytic fibroid rather than an adnexal mass. However, sometimes this distinction can be difficult or impossible and then an exophytic uterine fibroid can mimic an adnexal mass (Figures 74.1–74.4) [1–3]. It is useful to remember the aphorism that “the commonest cause of an apparent solid adnexal mass at ultrasound is an exophytic fibroid.” Exophytic fibroids, like other fibroids, can undergo cystic degeneration, and can then mimic a cystic adnexal mass (Figure 74.2) [4–6].

Importance

The recognition that a mass adjacent to the uterus is an exophytic fibroid can be of major clinical importance, since it eliminates adnexal malignancy as a differential consideration. Occasionally an exophytic fibroid can torse and be a cause of pain. The finding of an exophytic fibroid with little or no enhancement on CT or MRI and with or without some degree of ascites in a patient with acute pelvic pain is suggestive of torsion (Figure 74.5) [7,8], remembering that a poorly enhancing mass adjacent to the uterus can be an ovarian fibroma (Figure 74.6). In the latter case, the history of acute pain will typically be absent.

Typical clinical scenario

Like other fibroids, exophytic fibroids are primarily seen in women of older reproductive age.

Differential diagnosis

Several imaging findings are helpful in the accurate characterization of an exophytic uterine fibroid:

• Identification of the ipsilateral ovary as a separate structure is probably the easiest and simplest way of establishing that a mass adjacent to the uterus is likely to be an exophytic fibroid.

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