PMC9357808_01
Magnetic resonance imaging (MRI) of the pelvis performed at 21 weeks of gestation. (a) Axial T1-weighted image. (b) Axial T2-weighted image. (c) Sagittal T2-weighted image. (d) Axial diffusion-weighted image (b factor: 1000 s/mm2). (e) Apparent diffusion coefficient (ADC) map. MRI shows a well-circumscribed teardrop-shaped cystic lesion with mural nodules measuring 68 x 45 x 35 mm in the right ovary. The cystic lesion shows uniformly marked high signal intensity on the T1-weighted image (a, asterisk) and intermediate signal intensity (b, asterisk) on T2-weighted images consistent with ovarian endometrioma. The mural nodules show intermediate to high signal intensity on T2-weighted images (b, c; short arrows) similar to the placenta (c, long arrows). Diffusion-weighted image (d, short arrows) and ADC map (e, short arrows) show the mural nodules with a high ADC value (1.6 x 10-3 mm2/s). Based on these imaging findings, we diagnosed a decidualized ovarian endometrioma.
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MRI for further evaluation showed a well-circumscribed, teardrop-shaped cystic lesion with mural nodules measuring 68 x 45 x 35 mm in the right ovary (Figure 1).
Magnetic resonance imaging (MRI) of the pelvis performed at 27 weeks of gestation. (a) Axial T1-weighted image. (b) Axial T2-weighted image. (c) Sagittal T2-weighted image. (d) Axial diffusion-weighted image (b factor: 1000 s/mm2). (e) ADC map. (f) Coronal T1-weighted image with fat saturation. The cystic lesion disappears (a-e). Ascites around the uterus shows high signal intensity on fat-suppressed T1-weighted images, which is consistent with bloody ascites (f, arrows). Based on serial MRI findings, rupture of the decidualized ovarian endometrioma is suspected.
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The decidualized ovarian endometrioma had disappeared; however, bloody ascites were found (Figure 2).
Microscopic view of a mural nodule (hematoxylin and eosin staining, magnification: 100x). Edematous tissue with abundant stromal cells' cytoplasm is visible (asterisk). These findings are consistent with decidualization.
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Histopathological findings revealed decidual reaction of the ovarian endometrioma and no evidence of malignancy (Figure 3).