The uncertainty of the diagnosis can be related to atypical imaging findings due to altered morphology or structure or unusual flow patterns [20]. Uncommon enhancement patterns included the so-called flash-filling pattern mostly seen in small hemangioma and marked by intense and uniform enhancement on the arterial phase, hemangioma with perilesional enhancement secondary to arteriovenous shunting, and finally the hyalinized or sclerosed hemangioma with loss of the typical globular enhancement on contrast-enhanced studies related to the replacement of the vascular spaces by hyalinized fibrotic tissue. Sometimes in large hemangiomas, thrombosis of sectorial or lobar portal branch is associated (Fig. 11.2).

Recently, Portolani et al. [21] analyzed 28 patients with liver cancer who were observed after an initial erroneous diagnosis of hemangioma. The authors reported that the majority of the incorrect diagnoses (75 %) came from low volume center and occurred more frequently with the small nodules in chronic liver disease. For these reasons, as reminded by Duran et al. [22], all cases of hemangioma should be confirmed with at least one MR after 3–6 months, especially in cases of atypical pattern of hemangioma and in chronic liver disease. In situation at risk of having the error (low volume center, poor quality of imaging, etc.), revision of the imaging by an expert radiologist is strongly recommended. On the other hand, it’s also possible to perform an overtreatment of a benign lesion because of a false diagnosis of malignancy. Shimizu et al. [23] reported that hemangioma was the most frequent final diagnosis on 32 patients operated because of a false diagnosis of cancer. In a recent study, the authors showed that T2 shine-through effect is approximately observed in half of the lesions (mainly <1 cm) and in two-thirds of a large patient population with hepatic hemangiomas [22]. Radiologists should be aware of this phenomenon considering that T2 shine-through effect is commonly used to distinguish between benign and malignant lesions. Small solid liver tumors, which eluded preoperative radiological examinations, can be a difficult clinical problem for the surgeon. Intraoperative ultrasonography is crucial for accurate diagnosis [24]. At the intraoperative phase, ultrasonography hemangioma typically appears as a well-defined, lobulated, homogenous hyperechoic mass, but it can be also hypoechoic due to hemorrhage or fibrosis. It is known that small hepatocellular carcinomas and some liver metastases (from colorectal, neuroendocrine, and renal cancers) may also appear as hyperechoic lesions. The problem of differentiating benign from malignant lesions on intraoperative ultrasonography exploration becomes crucial. One useful test for diagnosing a hemangioma in cases of not typical ultrasonographic pattern is the finger compression of suspicious lesions. In fact, when compressed, the hemangioma changes in size and appearance (Fig. 11.3). Nevertheless, in cases of deep lesions or located in the posterior segments, the contrast-enhanced intraoperative ultrasonography provides more useful additional informations. The behavior of lesions during portal and delayed phases has been considered to be helpful in determining the nature of a nodule. The pattern of hypoenhancement in the late phases (washout) is typical of malignancies. In contrast, the benign lesions are isoenhancing or hyperenhancing as hepatic hemangioma [25].