Tsuboyama Takahiro, Fukuzawa Takuya, Nakaya Moto, Toyama Yasuchiyo, Ohya Ayumi, Sano Katsuhiro, Takahata Akiko, Kido Kansuke, Tomiyama Noriyuki
Kobe University, Kobe, Japan.
Osaka University, Osaka, Japan.
Abdom Radiol (NY). 2025 Jan;50(1):538-547. doi: 10.1007/s00261-024-04535-x. Epub 2024 Aug 21.
Placental site trophoblastic tumor (PSTT) is a rare form of gestational trophoblastic neoplasm with few previous imaging case reports. We report multiparametric MRI findings in four cases of PSTT with special emphasis on the "pseudo-myometrial thinning" underlying the tumor.
We reviewed multiparametric MRI and pathologic findings in four cases of PSTT from four institutions. Signal intensity, enhancement pattern, margins, and location of the tumors were evaluated, and myometrial thickness underlying the tumor and normal myometrial thickness contralateral to the tumor were measured on MRI. The myometrial thickness underlying the tumor was also measured in the resected specimen and compared with the myometrial thickness measured on MRI using the Friedman test.
All tumors showed heterogeneous signal intensity on T1-weighted imaging, T2-weighted imaging (T2WI), and diffusion-weighted imaging. Three of the four tumors had a hypervascular area on dynamic contrast-enhanced (DCE) MRI. A hypointense rim on T2WI and DCE-MRI was seen in all tumors. All tumors protruded into the uterine cavity to varying degrees and extended into the myometrium close to the serosa. The myometrial thickness underlying the tumor measured on MRI (median thickness, 1.2 mm) was significantly thinner than that measured on pathology (median thickness, 9.5 mm) and normal myometrial thickness contralateral to the tumor on MRI (median thickness, 10.3 mm) (P = 0.02), and there was no significant difference between the latter two.
The thickness of the myometrium underlying the tumor on MRI was approximately one tenth of the thickness on pathology. Thus, the tumors appeared to have almost transmural invasion even when pathologically located within the superficial myometrium. This "pseudo-thinning" of the underlying myometrium and the hypointense rim on MRI could be caused by focal compression of the myometrium by the tumor, possibly due to the fragility of the myometrium at the placental site.
胎盘部位滋养细胞肿瘤（PSTT）是妊娠滋养细胞肿瘤的一种罕见形式，既往影像学病例报道较少。我们报告4例PSTT的多参数MRI表现，特别强调肿瘤下方的“假肌层变薄”。
我们回顾了来自4家机构的4例PSTT的多参数MRI和病理结果。评估了肿瘤的信号强度、强化方式、边界和位置，并在MRI上测量了肿瘤下方的肌层厚度以及肿瘤对侧的正常肌层厚度。还在切除标本中测量了肿瘤下方的肌层厚度，并使用Friedman检验将其与MRI上测量的肌层厚度进行比较。
所有肿瘤在T1加权成像、T2加权成像（T2WI）和扩散加权成像上均表现为不均匀信号强度。4个肿瘤中有3个在动态对比增强（DCE）MRI上有高血管区域。所有肿瘤在T2WI和DCE-MRI上均可见低信号边缘。所有肿瘤均不同程度地突入子宫腔并延伸至靠近浆膜的肌层。MRI上测量的肿瘤下方肌层厚度（中位数厚度，1.2mm）明显薄于病理测量值（中位数厚度，9.5mm）和MRI上肿瘤对侧的正常肌层厚度（中位数厚度，10.3mm）（P = 0.02），后两者之间无显著差异。
MRI上肿瘤下方的肌层厚度约为病理厚度的十分之一。因此，即使在病理上位于浅表肌层内，肿瘤似乎也几乎有透壁浸润。这种肿瘤下方肌层的“假变薄”以及MRI上的低信号边缘可能是由于肿瘤对肌层的局灶性压迫所致，可能是因为胎盘部位肌层的脆弱性。
