21 Finally, cystic adenomyosis, widely regarded as the rarest subtype, involves cystic adenomyomas in the myometrium, which contain endometrial tissue (13). Figure 1.1 shows examples of these subtypes on MRI. Figure 1.1: Examples of MRI subtypes (on MRI), A. Focal adenomyosis concentrated in the posterior wall (red arrow) B. Diffuse adenomyosis affecting the whole uterine wall C. Cystic adenomyosis with islands of endometrial tissue in the myometrium (largest cystic focus circled in red). (Images taken from own study populations). Whilst the aforementioned subtypes are most commonly reported in the literature, some authors (14–18) have further made the distinction between adenomyosis of the inner myometrium (AIM) and adenomyosis of the outer myometrium (AOM). Here, the inner myometrium refers to the inner one third of the myometrium closest to the endometrium, and the outer myometrium refers to the outer two thirds (see Figure 1.2). Similarly, AIM can also be referred to as adenomyosis interna, and AOM as adenomyosis externa. This classification system can also be combined with the former, where an adenomyosis lesion could also be described as ‘focal adenomyosis of the outer myometrium’ (FAOM) (12) for example.
RkJQdWJsaXNoZXIy MTk4NDMw