Hemangiomas are a benign proliferative congenital vascular malformation that originate from the embryonic sequestrations of mesodermal tissue and can be found in any organ. They have an incidence of approximately 2%-3%(2, 4). While intestinal hemangiomas are well-known and have previously been described in the literature, mesenteric hemangiomas represent one of the rarest sites for hemangiomas. Mesenteric hemangiomas may originate either from the bowel wall and the mesentery, or the mesentery alone(7). We herein report a case of a mesenteric hemangioma that presented with an anomalous vein that arose from the superior mesenteric vein and extended down to the mesorectum. These findings suggest that, in this case, the mesenteric hemangioma originated in the mesentery and ultimately involved the intestinal wall.
Clinical presentations and diagnoses of mesenteric hemangiomas depend on their size, localization, and intestinal wall involvement. Smaller tumors are often asymptomatic whereas symptomatic masses tend to be large at the time of diagnosis. Larger hemangiomas located in the mesentery can cause intraperitoneal hemorrhage and can often result in life-threatening conditions. When mesenteric hemangiomas involve the bowel wall, they may result in intraluminal bleeding. Therefore, the clinical manifestations are hematemesis or melena. Long-term chronic occult blood loss is an important cause of anemia.
Currently, radiological evaluation plays an important role in the noninvasive examination of abdominal diseases, including mesenteric hemangioma. Imaging examinations, such as CT and MRI, cannot be used to unequivocally diagnose mesenteric hemangiomas, but they do allow a more precise evaluation of the size, vascularization, and possible involvement of adjacent structures of the tumor(7). Calcifications were seen scattered throughout the lesion on CT. Some studies suggested that this was due to degenerative changes as a consequence of the thrombosis within the sinuses, caused by perivascular inflammation and stasis of blood flow(4, 11). Other studies have shown that calcifications may ultimately form phleboliths, which represent an important diagnostic feature, seen in 26 to 50% of affected adult patients(4). Phleboliths are usually signal voided on both Tl and T2 weighted images, and thrombosed vessels show serpiginous structures with high signal intensity on MRI(11). An important imaging finding in our case suggested that a mesenteric hemangioma originated from the mesentery rather than the bowel wall, which is different from some reported cases. A contrast-enhanced portal venous phase CT scan showed an anomalous vein arising from the superior mesenteric vein and extending down to the mesorectum. Image examination also revealed transmural thickening of the wall of the involved bowel loops. On CT hemangiomas may be homogeneous or heterogeneous with possible cystic structures. The heterogeneity of hemangiomas may be due to intralesional degeneration consisting of hemorrhage, fibrosis, or calcification(2). On MRI, hemangiomas usually have an iso- or hypo-intense signal on T1-weighted images. On T2-weighted images, hemangiomas typically show high signal intensity and are more clearly depicted with fat suppression. Degenerative changes, such as fibrosis, result in a heterogeneous signal intensity on T2-weighted images. Intratumoral hemorrhage may show hypointense signal on T2-weighted images, making hemangiomas hard to differentiate from other solid mesenchymal tumors, such as fibromas or leiomyomas (4). Characteristic discontinuous peripheral nodular progressive enhancement patterns can be seen in some mesenteric hemangiomas. However, enhancement may be heterogeneous or minimal or may be present only on delayed phases likely due to internal fibrotic changes(2).
A definitive diagnosis of cavernous hemangioma of the mesentery depends on histopathological examination. Because of the high risk of hemorrhage, biopsy of clinically suspected hemangiomas is not recommended. Histologically, cavernous hemangiomas are composed of dilated vessels of varying sizes, which are lined with flattened endothelial cells with little fibrous connective tissue between the vascular channels. The vessel lumen often shows thrombosis and contains a large number of erythrocytes(9, 13, 14). To avoid the risk of bleeding during biopsy, we used immunohistochemistry to diagnose our patient. The results were positive for CD34, but were negative for the lymphatic endothelial marker D2-40. CD34 is expressed not only in vascular endothelial cells, but also in lymphatic endothelial cells, while D2-40 is only expressed in lymphatic endothelial cells. Combined with vascular tumor suggested by histology, the diagnosis of cavernous hemangioma was made. In addition, CD31 is vascular endothelium-specific, and is often as a diagnostic marker of hemangioma(5, 9).
The optimal treatment of mesenteric hemangiomas is surgical resection of the mesenteric lesion and the involved intestinal segments (3, 8). Recurrence after complete resection are rare. Other nonoperative techniques, such as low-dose radiation therapy, cryotherapy, brachytherapy, sclerotherapy or interventional angiography, often result in symptom recurrence and are therefore only temporary solutions(3, 4).