kaposiform hemangioendothelioma

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Kaposiform hemangioendothelioma is a rare, locally invasive vascular tumor that often presents in infancy, most commonly as an enlarging cutaneous mass .

Epidemiology

Kaposiform hemangioendothelioma is a rare disease of childhood. The exact incidence and prevalence has not been accurately determined, but has been estimated to be 0.07 and 0.91 per 100,000 children per year, respectively, based on cases at a large referral center . Kaposiform hemangioendothelioma has no gender predilection and most commonly presents in the first year of life, but there are reports of development in later life .

Clinical presentation

The majority of patients present with an enlarging cutaneous mass that may have red/purple cutaneous markings and telangiectasia. Other cutaneous presentations include erythematous plaques, patches or nodules. Non-cutaenous involvement can result in non-specific sympatomatology depending on the organs involved .

Larger lesions, especially intrathoracic/intra-abdominal lesions may present with Kasabach-Merritt phenomenon, which is characterized by coagulopathy and thrombocytopenia caused by platelet trapping in the vascular tumor .

Lesions are locally aggressive however the tumor is not known to metastasize .

Pathology

Kaposiform hemangioendothelioma is a neoplasm arising from endothelial cells.

Etiology

Genetic factors are thought to play a role in disease development but the exact cause has not been determined.

Location

Kaposiform hemangioendotheliomas can occur anywhere in the body but have a predilection for the trunk and extremities. They most commonly present in subcutaneous tissue and tend to cross tissue planes involving fascia, muscle, bone and other structures .

Classification
Macroscopic appearance

Kaposiform hemangioendotheliomas grossly appear as infiltrating nodules/masses. Sizes vary from small nodules or plaques to massive infiltrating tumors. Lesions often show a purple/red coloration. Intra-thoracic and intra-abdominal lesions tend to be larger and more infiltrative than peripheral lesions .

Microscopic appearance

Characteristic histopathology shows spindle cells aligned in sheets or nodules forming vascular-like channels largely involving the subcutaneous tissues .

Immunophenotype

Immunohistochemistry shows positivity for CD31, CD34 and D2-40 (lymphatic marker) .

Radiographic features

CT

Lesions show a homogenous mass with ill-defined margins, often with extension into surrounding structures. Unenhanced CT often demonstrates homogenous masses with iso-attenuation to adjacent muscle and heterogenous enhancement with contrast administration .

MRI

On T1-weighted images, lesions are hypointense and typically show poorly circumscribed soft tissue masses and diffuse enhancement with contrast .

Lesions are heterogenous, hyperintense masses on T2-weighted images, with heterogeneous enhancement with contrast administration .

Ultrasound

Lesions are largely hyperechoic ill-defined masses with increased vascularity .

Treatment and prognosis

If patients are symptomatic and lesions are amenable to surgical resection, this remains the treatment option of choice and can be curative. Lesions that are asymptomatic and have no vital organ involvement may benefit from a period of observation, as spontaneous regression may occur without treatment .

In unresectable lesions with significant organ involvement or functional compromise, no current consensus exists for medical therapies. However, the use of prednisolone along with anti-neoplastic and immunomodulatory agents (vincristine, sirolimus) is common .

Differential diagnosis

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