## Distinguishing Fibroids from Adenomyosis ### Key Structural Difference **Key Point:** Fibroids are discrete, well-demarcated benign tumors arising from myometrial smooth muscle, whereas adenomyosis is diffuse infiltration of endometrial glands into the myometrium. ### Comparison Table | Feature | Fibroid | Adenomyosis | | --- | --- | --- | | **Morphology** | Discrete nodular masses | Diffuse, poorly demarcated | | **Imaging finding** | Well-defined masses, whorled pattern on MRI | Junctional zone thickening, heterogeneous signal | | **Uterine size** | Irregular, asymmetric enlargement | Uniform, symmetrical enlargement | | **Consistency** | Firm nodules | Boggy, tender | | **Dysmenorrhea** | Mild or absent | Severe, progressive | | **Menorrhagia** | Marked | Moderate to marked | | **Infertility** | Submucous fibroids → implantation failure | Adenomyosis → reduced receptivity | ### Clinical Pearl **Clinical Pearl:** On bimanual examination, fibroids present as discrete, hard, irregular nodules that can be felt separately from the uterine body. Adenomyosis causes uniform, boggy, tender enlargement without discrete masses. ### High-Yield Imaging Distinction **High-Yield:** MRI is the gold standard for differentiation: - **Fibroids:** Well-circumscribed masses with low T2 signal (whorled appearance), clear demarcation from normal myometrium - **Adenomyosis:** Ill-defined junctional zone thickening (>12 mm), high T2 signal intensity, "striated" or "cystic" appearance ### Why Option 0 is Correct The presence of **discrete nodular masses** is pathognomonic for fibroids. This finding on ultrasound or MRI definitively separates fibroids (focal lesions) from adenomyosis (diffuse process). The whorled, well-demarcated appearance on imaging is the single most reliable discriminator. [cite:Jeffcoate's Principles of Gynaecology Ch 19]
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