Kaposiform hemangioendothelioma

Last revised by Joachim Feger on 15 Dec 2022

Kaposiform hemangioendotheliomas are rare, locally invasive vascular tumors that often present in infancy, most commonly as an enlarging cutaneous mass 1,2. They are currently classified as distinct from tufted angiomas in the ISSVA classification of vascular anomalies. However, some consider it to be on one spectrum and in the WHO classification of soft tissue tumors they are listed under one heading 3.

Alternative terms such as ‘Kaposi-like infantile hemangioendothelioma’, ‘hemangioma with Kaposi-like features’, and ‘angioblastoma of Nakagawa’ are no longer recommended 3.

Kaposiform hemangioendotheliomas are a rare disease of childhood. The exact incidence and prevalence have not been accurately determined, but have been estimated to be 0.07 and 0.91 per 100,000 children per year, respectively, based on cases at a large referral center 2. Kaposiform hemangioendothelioma has no gender preference and most commonly presents in the first year of life, but there are reports of development in later life 2.

The diagnosis of kaposiform hemangioendothelioma is often difficult to establish by typical clinical, imaging,  histologic and immunohistochemical characteristics 4.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 3:

  • indistinct merging nodules made of fascicles of plump endothelial spindle cells with slit-like erythrocytes containing gaps

  • surrounding collagenous stroma in the periphery with prominent dilated lymphatic vessels

  • immunopositivity for CD31, ERG, CD34 and lymphatic markers like podoplanin, LYVE1 and PROX1

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-cutaneous involvement can result in non-specific symptomatology depending on the organs involved 1,2,5.

More extensive lesions, especially intrathoracic/intra-abdominal lesions may present with the Kasabach-Merritt phenomenon, which is characterized by coagulopathy and thrombocytopenia caused by platelet trapping in the vascular tumor 2.

Lesions are locally aggressive however the tumor is not known to metastasize 6.

Kaposiform hemangioendotheliomas are often deep-seated vascular neoplasms composed of lobules of capillaries and spindled endothelial cells associated with lymphatic vessels 3.

Genetic factors are thought to play a role in disease development ref but the exact cause has not been determined 3.

Kaposiform hemangioendotheliomas can occur anywhere in the body but have a predilection for the trunk and extremities. They are most commonly present in the subcutaneous tissue and tend to cross tissue planes involving fascia, muscle, bone and other structures 5.

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 5,6.

Characteristic histopathology shows the following 3:

  • ill-defined coalescing nodules  of spindled endothelial cells

  • slit-like erythrocyte containing lumina

  • surrounding by peripheral fibrosis with dilated crescentic lymphatic vessels

  • possible perineural invasion

Immunohistochemistry shows positivity for CD31, CD34 and lymphatic markers such as podoplanin (D2-40), LYVE1 and/or PROX1 3,6.

Lesions are largely hyperechoic ill-defined masses with increased vascularity 7.

Lesions show a homogeneous mass with ill-defined margins, often with extension into surrounding structures. Unenhanced CT often demonstrates homogeneous masses with iso-attenuation to adjacent muscle and heterogenous enhancement with contrast administration 6,7.

On T1-weighted images, lesions are hypointense and typically show poorly circumscribed soft tissue masses and diffuse enhancement with contrast 7.

Lesions are heterogenous, hyperintense masses on T2-weighted images, with heterogeneous enhancement with contrast administration 7.

The radiological report should include a description of the following:

  • form, location and size

  • tumor margins

  • relation to muscular fasciae and skeletal muscles in soft tissues

  • relationship to local nerves and vessels

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 9.

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 9,10.

Kaposiform hemangioendothelioma has been identified as a distinct entity by the American pathologists Lawrence R. Zukerberg, Brian J. Nickoloff and Sharon W. Weiss in 1993 1,4.

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