Microscopic description and IHC:
Histologically, there are numerous blood filled vessels lined by a simple endothelium without cytologic atypia. Some of the vessels are compressed by the surrounding stroma, which has a loose myxoid to sclerotic appearance. Additionally, there are extravasated red blood cells and scattered hemosiderin deposits.
Discussion:
Sclerosing hemangioma of the liver is a rare neoplasm that can be difficult to distinguish radiologically from lesions such as hepatocellular carcinoma, cholangiocarcinoma, metastasis and abscess. They are typically found in sixty to seventy year old patients, and it is predominantly found in males (67%). Vague abdominal symptoms such as pain, fullness, indigestion and distention can accompany them.
Radiologically, it shows mild to moderate hyperintensity on T2 weighted MR images with patchy enhancement during the arterial phase and gradual progressive enhancement during the portal and delayed phases.
The microscopic features of this neoplasm include blood-filled, dilated and thin-walled vessels. The vessels are often collapsed. The vessels are lined by a single layer of flat epithelium with no mitotic activity or atypia. There is varying degrees of stromal fibrosis, sometimes with a sclerotic center and patent vessels along the periphery. A loose myxoid matrix and a concentric cuff of stellate cells sometimes surrounds the vascular channels. Recent hemorrhages, hemosiderin, calcifications and infarction can also be seen.
Immunohistochemistry is not necessary for diagnosis, but would demonstrate strong positive staining for endothelial cell markers, factor VIII related antigen, CD34 and CD31.
Within the differential diagnosis, cavernous hemangioma has more dilated vessels and lacks the sclerotic stromal background. Angiomyolipoma contains adipose tissue and smooth muscle, in addition to thick-walled vessels. Finally, solitary fibrous tumor is composed of interlacing fascicles of spindle cells, sometimes with associated myxoid changes, fibrosis and hyalinization.
There are two theories on the pathogenesis of sclerosing hemangiomas. The first theorizes that minor hemorrhage and thrombosis within a hemangioma instigates fibrotic progression to a sclerosing hemangioma. There are previous reports of sclerosing hemangiomas arising within cavernous hemangiomas. The second theory proposes that mast cells play an integral role in the development of this tumor. Overall, these are benign tumors then tend to be stable and can be followed without treatment. Symptoms tend to arise when the tumors reach sufficient size, which may warrant surgical intervention.