Kaposiform hemangioendothelioma (KHE)

Overview

Kaposiform hemangioendothelioma (KHE) is a benign tumor of the blood vessels. It typically grows just below the skin or, more rarely, into internal organs, between the lungs or in the abdominal cavity. This rare condition mainly affects infants and young children, although cases have been reported in older children and adults.

KHE tumors are not cancerous. However, in about 70 percent of cases, a serious complication called Kasabach-Merritt phenomenon (KMP) develops. This complication causes rapid tumor growth and a sharp drop in the number of platelets in the blood, which affects the blood's ability to clot after an injury. Blood clots may form in the small blood vessels, interfering with normal blood flow to the tissues.

The risk of developing Kasabach-Merritt phenomenon is higher if the tumor is:

• Large
• Present at birth
• Located in the abdominal cavity or between the lungs

KHE tumors will eventually stabilize and stop growing. In rare cases, they may shrink on their own. KHE is treated with medication, surgery or both.

A related condition, called tufted angioma, produces similar symptoms but is less likely to lead to Kasabach-Merritt phenomenon.

Signs & symptoms

In about half of all cases, the tumor is present at birth. Otherwise, it usually develops before the first birthday.

A KHE tumor looks like a slightly raised mass with a bruised appearance. Occasionally, tiny, threadlike red lines — commonly referred to as spider veins — are visible. The tumor may also sweat more and appear hairier than surrounding areas.

The most common tumor locations are the arms and legs, although tumors can also form on the trunk, head or neck. Over time, the tumor hardens and turns a red-purple color. In some cases, the tumor may grow to cover a child's entire limb.

KHE tumors in the abdominal cavity or between the lungs can give the skin above it a mottled, bluish-purple appearance.

If Kasabach-Merritt phenomenon develops, the first sign is rapid growth of the tumor, which will become painful. The tumor will have a purple or brownish-red, spotty appearance, which is caused by bleeding beneath the skin.

Diagnosis

We have seen many cases of KHE at the Birthmarks and Vascular Anomalies Center. If we suspect a patient has this condition, we will obtain blood tests, and may use a magnetic resonance imaging test (MRI) and possibly a biopsy to help make a diagnosis.

Treatment

Medications are usually very effective in treating this condition. Our BVAC specialists help administer and monitor these medications. Occasionally we decide surgically removing the tumor is the best treatment option.

Medications we often use for this condition include the following:

• Aspirin to help decrease clotting, especially in less severe cases
• Sirolimus, an oral medication, which works quickly to improve clotting and decrease tumor growth
• Replacement of clotting factors and intravenous transfusions, if indicated
• Medications such as Vincristine, a chemotherapy drug, and oral cortisone medications are used less often

Each child's treatment will be tailored to his or her specific case.