肝局灶性结节增生（FNH）【双语病例】 Focal nodular hyperplasia （FNH）病例选自《Mayo Clinic Body MRI Case Review》转自：双语学影像Fig 1.11.1Fig 1.11.2HISTORY:21-year-old woman with aliver mass identified incidentally on CT during workupfor acute appendicitis21岁女性，因阑尾炎行CT检查，发现肝脏肿块。
IMAGING FINDINGS:Axial fat-suppressed FSE T2-weighted image (Figure 1.11.1)demonstrates a large right hepatic lobe mass with mild hyperintensity relative to liver and a high intensity central scar. IP and OP T1-weighted 2D SPGR images showed no signal dropout to suggestintravoxel fat (images not shown). Pregadolinium and arterial, portalvenous, equilibrium, and 5-minute delayed phasepostgadolinium 3D SPGR images (Figure1.11.2) demonstrate marked,uniform arterial phase enhancement within the lesion that rapidly becomes isointensewith liver. Note also gradual enhancement of the central scar, as well as peripheral rim enhancement.横断位T2WI FSE脂肪抑制序列(Figure 1.11.1)示肝右叶巨大稍高信号肿块肿块，内可见中央瘢痕，呈明显高信号。
2D SPGR T1WI同反相位图像未见明显信号衰减，提示病灶内没有脂肪成分（图像未示出）。
3D SPGR增强扫描动脉期、门静脉期、平衡期及5分钟延迟扫描(Figure1.11.2)示动脉期明显均匀强化，然后信号迅速降低，门静脉期及平衡期病灶与肝实质呈等信号。
另外，中央瘢痕和病灶边缘呈渐进性强化。
DIAGNOSIS:Focal nodular hyperplasia局灶性结节增生COMMENT:FNH is the second most common benign tumor of the liver afterhemangiomas, accounting for 8% of these lesions and with an estimated prevalence of 0.9%。
FNHs consist of hyperplastic hepatocytes and small bile ductules surrounding a fibrovascular central scar that is thought to represent a hyperplastic response to a preexisting vascular malformation rather than a true neoplasm. They are more prevalent in women(usually of reproductive age) than men by an 8:1 ratio and are solitary in 80% to 95% of cases. Since FNHs are benign non-surgical lesions, the most important job of the imager is to make a confident diagnosisand distinguish them from more potentially unfriendly hypervascular lesions, such as adenoma, HCC, and metastases.Most of the time, this is relatively easy to accomplish.FNH是仅次于血管瘤的肝脏第二常见良性肿瘤，约占全部肝肿瘤的8%，发病率约为0.9%。
FNH主要由增生的肝细胞、小胆管包绕中心纤维血管瘢痕构成，一般认识是血管畸形基础上的增生性病变，而非真正的肿瘤。
FNH女性多于男性，男女比例约8:1，且通常发生于育龄妇女。
单发病灶多见，约占全部的80%-95%。
由于FNH是良性病变，不需要手术治疗，所以对于放射科医师来说，最主要的任务是明确诊断，与其他富血供潜在恶性肿瘤相鉴别，如腺瘤、HCC、转移瘤等。
通常FNH的诊断和鉴别诊断并不难。
Classic FNHs (illustrated by this case) are described as invisible or barely perceptible lesions except on postgadolinium arterial phase images; they are typically isointense to liver on T1-weighted images and isointense or mildly hyperintense on T2-weighted images. It is true, however, that FNHs are often at least moderately hyperintense on diffusion-weighted images, which illustrates the general principle that DWI is a technique better used for lesion detection than lesion characterization.Dynamic postgadolinium images show intense uniform enhancementon arterial phase images, which quickly becomes nearly isointense to liver on portal venous and equilibrium phaseimages. The central scar (seen in this case but not universally identifiable) generally shows high signal intensity on T2-weighted images and gradual enhancement following gadolinium administration. An elaborate set of imaging characteristics of the central scar has been described in the literature as a means of distinguishing FNH from fibrolamellar hepatoma; however, the percentage of lesions thatdon’t follow the rules is high enough that we rarely find these guidelines particularly useful.典型的FNH(如本例患者)在T1WI呈等信号，T2WI呈等或稍高信号，所以除了增强扫描动脉期外，有时难以发现。
然而在DWI图像上，病灶通常呈高信号，说明DWI在病灶的发现上作用大于定性诊断。
动态增强扫描，动脉期病灶明显强化，门脉期及延迟期病灶与肝实质呈等信号。
病灶中央瘢痕（本例患者可见，但并非全部可见）常呈T2WI 高信号，增强扫描渐进性强化。
中央瘢痕的这种典型表现通常作为FNH与纤维板层样肝癌的鉴别点，但很多的病例的表现并不如此典型，所以这一原则并非特别实用。
This case illustrates the appearance of a very large, but otherwise typical, FNH,obtained with a standard extracellular gadolinium-based contrast agent. The examination was done several years ago and exemplifies one of the problems of advancing technology: We read this case as consistent with FNH and offered no differential diagnosis. If it were to appear today,however, the report likely would containa differential that included adenoma (the hedge isthe radiologist’sfavorite plant) and suggest that a follow-up examination with a hepatobiliarycontrast agent be performed (although the absolutely classic appearance of the central scar might provide enough assurance for bold radiologists to remain firm in their conviction). This is entirely unnecessary; we used to be very certain about what FNH looked like usingstandard extracellular gadolinium contrast agents and were rarely mistaken. Although it is true that small adenomas can have a nearly identical appearance to FNH, they aren’t verycommon and it’s not clear whether missing one of these lesions results in any actual harm.此例患者病灶体积较大，但细胞外造影剂增强扫描图像非常典型。