Kaposiform haemangioendotheliomas are rare, locally invasive vascular tumours that often present in infancy, most commonly as an enlarging cutaneous mass 1,2. They are 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 tumours they are listed under one heading 3.
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Terminology
Alternative terms such as ‘Kaposi-like infantile haemangioendothelioma’, ‘haemangioma with Kaposi-like features’, and ‘angioblastoma of Nakagawa’ are no longer recommended 3.
Epidemiology
Kaposiform haemangioendotheliomas 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 centre 2. Kaposiform haemangioendothelioma has no gender preference and most commonly presents in the first year of life, but there are reports of development in later life 2.
Diagnosis
The diagnosis of kaposiform haemangioendothelioma is often difficult to establish by typical clinical, imaging, histologic and immunohistochemical characteristics 4.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue and bone tumours (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
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-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 characterised by coagulopathy and thrombocytopenia caused by platelet trapping in the vascular tumour 2.
Lesions are locally aggressive however the tumour is not known to metastasise 6.
Pathology
Kaposiform haemangioendotheliomas are often deep-seated vascular neoplasms composed of lobules of capillaries and spindled endothelial cells associated with lymphatic vessels 3.
Aetiology
Genetic factors are thought to play a role in disease development ref but the exact cause has not been determined 3.
Location
Kaposiform haemangioendotheliomas 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.
Classification
Macroscopic appearance
Kaposiform haemangioendotheliomas grossly appear as infiltrating nodules/masses. Sizes vary from small nodules or plaques to massive infiltrating tumours. Lesions often show a purple/red colouration. Intra-thoracic and intra-abdominal lesions tend to be larger and more infiltrative than peripheral lesions 5,6.
Microscopic appearance
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
Immunophenotype
Immunohistochemistry shows positivity for CD31, CD34 and lymphatic markers such as podoplanin (D2-40), LYVE1 and/or PROX1 3,6.
Radiographic features
Ultrasound
Lesions are largely hyperechoic ill-defined masses with increased vascularity 7.
CT
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.
MRI
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.
Radiology report
The radiological report should include a description of the following:
form, location and size
tumour margins
relation to muscular fasciae and skeletal muscles in soft tissues
relationship to local nerves and vessels
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 9.
In unresectable lesions with significant organ involvement or functional compromise, no consensus exists for medical therapies. However, the use of prednisolone along with anti-neoplastic and immunomodulatory agents (vincristine, sirolimus) is common 9,10.
History and etymology
Kaposiform haemangioendothelioma 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.
Differential diagnosis
tufted angioma
other vascular malformations, including primary lymphoedema