PMC7414370_01
Transvaginal ultrasound images: (a) the tumor margin and the underlying myometrium were hyperechoic and well defined. Several small nodules within a large mass were isoechoic and hypoechoic compared to the normal uterine myometrium; (b) an anechoic unilocular cystic area within a small nodule was observed (indicated by the arrow).
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Several small nodules within a large mass were isoechoic and hypoechoic compared to the normal myometrium (Figure 1(a)). An anechoic unilocular cystic area within a small nodule was observed (Figure 1(b)).
Unenhanced pelvic MRI. (a) Sagittal T1-WI shows a tumor demonstrating isointensity with the normal myometrium. (b) Sagittal T2-WI showing a tumor with a nodule-in-nodule appearance within the myometrium. The small nodules show a low signal intensity at T1-WI and a high signal intensity at T2-WI. (c) Hypointense bands within the small nodules are signalized with an arrow on coronal T2-WI. (d) At diffusion-weighted imaging (b = 1000 ms/mm2), the small nodules show a higher signal intensity than the surrounding tumors, and the surrounding tumors show a relatively higher signal intensity than the normal myometrium. (e) Both small nodules and surrounding tumors show a low signal intensity in the apparent diffusion coefficient (ADC) map. The ADC values of the small nodule and main tumor are 0.73 and 0.82 (10-3 mm2/s), respectively.
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T1-WI and lower signal intensity than the normal myometrium at T2-WI (Figures 2(a) and 2(b)). Multiple elliptical nodules with a diameter of 2 cm were also observed inside the mass showing a higher signal intensity at T2-WI than the surrounding tumor, which appeared to present a "nodule-in-nodule" appearance. Thin hypointense rims delineatheddelineathed the small nodules and the tumor at T2-WI. A high signal intense area was observed within the ventral small nodule and thought to be a cystic area (Figure 2(b)). T2-WI (Figure 2(c)). The main tumor and most of the small nodules showed restricted water diffusion compared to the surrounding tissues, which means a high signal intensity at DWI (b = 1000 ms/mm2) (Figure 2(d)) and a low signal intensity at the apparent diffusion coefficient (ADC) map (Figure 2(e)). The ADC values of the small nodule and main tumor were 0.73 and 0.82 (10-3 mm2/s), respectively (Figure 2(e)). A part of the small nodule in the anterior part of the tumor did not show restricted diffusion (Figures 2(d) and 2(e)).
Dynamic contrast-enhanced T1-WI pelvic MRI: (a) precontrast; (b) postcontrast 20 s; (c) postcontrast 60 s; (d) postcontrast 180 s. In dynamic contrast-enhanced T1-WI, the small nodules are enhanced rapidly and stronger than the normal myometrium in the early phase and decrease gradually in the later phase to the level similar to that of the normal myometrium. In contrast, the larger mass is enhanced gradually and heterogeneously, but it is weaker than the normal myometrium.
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In contrast, the small nodules were enhanced rapidly and stronger than the normal myometrium in the early phase, but they decreased gradually in the later phase to the level similar to that of the normal myometrium (Figure 3).
Resected specimen. Many nodules are observed on the surface of the uterine body tumor. The nodules that are harder than the soft tumor have a nodule-in-nodule appearance.
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The surgically resected specimen had a large number of elastic and hard nodules within a flexible mass exhibiting a nodule-in-nodule appearance within the uterine myometrium, and the maximum diameter of the tumor was 45 mm (Figure 4).
Histopathological findings of a nodule-in-nodule appearance. Microscopic imaging at loupe magnification on the left side and microscopic (x20) images on the right side corresponds to a nodule-in-nodule appearance with hematoxylin and eosin (HE) staining at the top, cluster of differentiation (CD) 10 immunohistochemistry (IHC) staining at the middle, and desmin IHC staining at the bottom. Images on the right are the magnifications of the boxed area in the left-hand images. (a) HE staining at loupe magnification. (b) HE staining at x20 microscopic magnification. (c) CD10 IHC staining at loupe magnification. (d) CD10 IHC staining at x20 microscopic magnification. (e) Desmin IHC staining at loupe magnification. (f) Desmin IHC staining at x20 microscopic magnification.
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Histopathologically, the mass had a nodule-in-nodule appearance when viewed microscopically, as shown in Figure 5.
Histopathological findings of the nodule-in-nodule appearance. (a) In the small nodules, the boxed areas in Figure 5(b) (x20) are marked for further magnifications at the top left-side image. Inset squares B, C, and D are magnified in Figures 6(b) (x40), 6(c) (x20), and 6(d) (x20), respectively. (b) More densely packed endometrial stromal cells with a concentric arrangement of the small spiral arteriole-like vessels (indicated by arrows) exhibit an expansile growth pattern. (c) Sex cord-like elements are observed partially within some small nodules. (d) Peripheral areas around the small nodule are more loosely packed with endometrial stromal sarcoma (ESS) cells. Some areas are intermingled with the normal uterine myometrium. (e) ESS cells with the eosinophilic cytoplasm in hematoxylin and eosin (HE) staining are observed to be partially stained positive with cluster of differentiation (CD) 10 immunohistochemistry (IHC) markers. (f) ESS cells with the eosinophilic cytoplasm in HE staining are observed to be partially stained positive with desmin IHC markers. (d), (e), and (f) images result in the diagnosis of low-grade endometrial stromal sarcoma (LG-ESS) with smooth muscle differentiation.
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Furthermore, sex cord-like elements were partially observed (Figure 6(c)) within some small nodules. The peripheral area around the small nodules and the large nodule that showed loosely packed ESS cells comprised a part of the main tumor (Figure 6(d)). It also partially stained positive with both IHC markers CD10 (Figure 6(e)) and desmin (Figure 6(f)), which resulted in a diagnosis of LG-ESS with smooth muscle differentiation.