CH most commonly affects the skin, mucosa and liver but can rarely occur in the retroperitoneal space. Several reports of CH originating from retroperitoneal organs (for example, adrenal gland, kidney and pancreas) are available, but primary retroperitoneal CH is even rarer [
1,
2]. CH is essentially a benign neoplasm that produces clinical symptoms only when the tumor compresses an adjacent organ or tissue. Most reported cases of retroperitoneal CH involve symptoms of abdominal pain when the tumor grows to a large size (for example, approximately 10cm in diameter). However, most cases of CH are asymptomatic and are only incidentally detected on routine imaging, as occurred in our present case. Based on the tumor location, MRI findings and abnormal catecholamine studies in our present case, we could not rule out paraganglioma and elected to utilize surgical resection as the treatment strategy. In regard to imaging findings, our present case showed relatively slow and weak enhancement on CT imaging, and enhancement was patchy in the peripheral area of the tumor compared with paraganglioma. This observation may be a diagnostic feature that is specific to retroperitoneal CH and could be used to differentiate retroperitoneal CH from paraganglioma. However, the CT findings of retroperitoneal CH have not been extensively characterized [
3,
4]. Further, CT findings of CH may differ depending on the organ of origin. For example, typical CH of the pancreas shows strong contrast enhancement when compared with that of normal pancreas tissue [
5]. He
et al. described a well-encapsulated retroperitoneal CH without enhancement of the inner component [
2]. Similar to CT, MRI findings of retroperitoneal CH have not been well established. In general, CH shows low signal intensity on T1-weighted images and relatively high signal intensity on T2-weighted images. However, the degree of signal intensity might vary depending on the specific tumor component. Despite the availability of various imaging modalities, the differential diagnosis of retroperitoneal tumors adjacent to renal hilum still includes neurogenic tumors (for example, neuroganglioma, schwannoma), and lymphangiogenic tumors, (for example, lymphoma, IgG4-related disease), and other rare soft tissue tumors (for example, sarcomas). Thus, accurate pre-treatment diagnosis of retroperitoneal tumors remains difficult [
6].
Usually, watchful waiting is a common treatment strategy for asymptomatic and small CHs. In fact, hepatic CH is treated only when the tumor is large or produces symptoms. However, Forbes reported spontaneous rupture of adrenal hemangioma, which manifested as severe pain and hypotension [
7]. Further, Takeda
et al. reported rapidly growing CH with continuous abdominal pain [
8]. In addition, as in our present case, a diagnosis of paraganglioma or other malignant tumors is often difficult to exclude. These observations indicate that routine follow-up and adequate therapeutic intervention are sometimes required even for small retroperitoneal CHs. As for the therapeutic intervention, surgical resection could be the only and most effective treatment for retroperitoneal tumors at the moment. Other treatment modalities, for example, kinds of molecular targeted therapy, chemotherapy or radiation therapy, are tentatively applied for a small portion of cases.
In our present case, the laparoscopic approach was utilized for tumor resection. Since the tumor was located close to large vessels, (that is, left renal hilar vessels and abdominal aorta), meticulous manipulation was required and surgical resection might be challenging for this type of tumor. However, a laparoscopic procedure under magnified view can be a reasonable and safe approach when conducted by an experienced surgeon. In addition, postoperative recovery is much faster after laparoscopic resection when compared with recovery after open laparotomy. However, unexpected tumor adhesion or invasion can sometimes be appreciated during the laparoscopic approach, and these findings often necessitate conversion to an open approach. Recent studies suggest that laparoscopic resection is a safe and feasible operative approach for hemangioma of the adrenal gland or for paraganglioma [
9,
10]. Thus, the laparoscopic approach might represent a new standard operative procedure for the surgical management of retroperitoneal tumor. More precise preoperative diagnosis of retroperitoneal tumors would be of benefit to facilitate selection of the optimal treatment strategy.