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Original Paper: Clinical study

Management of Kasabach–Merritt Phenomenon With Transarterial Embolization in Patients With Kaposiform Hemangioendothelioma

Case Series

Celis-Jiménez, Alejandro; Meza-López, Ana Sofía; Santana-Cárdenas, Carmen Leticia; Cortés-Barrios, Delma Gabriela; Requena-Torres, Bertha Graciela; Tiznado-García, Héctor Manuel

Author Information
Journal of Vascular Anomalies: September 2021 - Volume 2 - Issue 3 - p e014
doi: 10.1097/JOVA.0000000000000014



Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor that is characterized by abnormal angiogenesis with a rapid and aggressive evolution. It is frequently associated with the Kasabach–Merritt Phenomenon (KMP) which is defined as a consumptive coagulopathy that presents with hypofibrinogenemia, as well as thrombocytopenia and microangiopathic anemia.1 This phenomenon can manifest as an intralesional hemorrhage as well as hemorrhages in other organ systems, and it renders a high-mortality rate in these patients.2–4 KHE can frequently be misdiagnosed as an infantile hemangioma due to its macroscopic similarities, nevertheless the latter is not associated with KMP, and macroscopically, it usually does not manifest with skin lesions such as erythematous to purple papules, plaques, nodules, or indurated tumors.1,3,5,6 Although the gold standard for diagnosis is made by biopsy, clinical and radiological features in magnetic resonance imaging such as the demonstration of a hyper vascular mass with feeding vessels, cutaneous thickness, and lymphedema depending on the tumor area are often sufficient.2 Previous consensus and current knowledge guide the management of pharmacological treatment with corticosteroids plus either sirolimus versus vincristine. Both dual therapies show promising results in the long term, although vincristine as monotherapy is successful in 60%–70% of patients.7 Sirolimus has been proved as an efficacious and safe treatment.8 It increases platelet count and decreases tumor size after an average treatment period of 6 months, although many patients still show platelet count decrease and progressive enlargement of tumor even after initiating treatment course with sirolimus.9 Although propranolol has been also proposed as an adjuvant pharmacological treatment due to its vasoconstrictive properties and its inhibition toward the vascular endothelial growth factor (VEGF), it is not effective in KHE.10 The surgical therapeutic approach with total excision of the tumor is curative as a result of the blood flow decrease and therefore the erythrocyte and platelet entrapment. Nevertheless, these patients are at high risk of trans-surgical hemorrhage either in the tumor itself or in other organ systems and the percentage of total excision due to the infiltrative nature of the tumor. Blood flow cessation has demonstrated significant improvement in KMP and lower risk of hemorrhage, but surgery is not intended to be the first-line treatment due to its long-term morbidity; therefore, therapeutic invasive approaches such as endovascular interventions with transarterial embolization of feeding vessels have showed promising temporary results according to previous case reports.3,11 The purpose of this article is to present a series of 4 cases of patients with KHE and KMP who were treated with transarterial embolization to show the significant improvement in serum hemoglobin and total platelet count as well as clinical manifestations at an immediate 48-hour control and sustained follow-up for at least 6 months.


We searched for clinical registers, medical records, progress notes, and consult visits of patients in the Pediatric Area of Unidad Médica de Alta Especialidad Centro Médico Nacional de Occidente that met the next inclusion criteria: pediatric patients with clinical diagnosis of KHE, anemia (World Health Organization definition for anemia in children: <11 g/dL) and thrombocytopenia (defined as total platelet count of <150 000 per µL) associated to KMP both of them proved by laboratory results at the time of admission to the hospital unit, and patients who were intervened with transarterial embolization. The following were listed in each patient’s case resume: sex, age at the moment of endovascular intervention, anatomical region of the tumor, comorbidities, previous pharmacological treatment, specifications of endovascular intervention and material used to embolize the feeding arteries as well as images of the procedures, medical treatment administered after the embolization, and laboratory follow-up at 48 hours, 1 week, 1 month, 3 months, and 6 months after each embolization. Only patients’ serum hemoglobin and platelet total count were taken into account for follow-up since not all patients had a record of fibrinogen at the desired follow-up timing. All of the patient’s parents gave informed consent to access medical records as well as patient’s procedure DICOM images and tumor photographs.


Only 4 patients met the inclusion criteria, 1 woman and 3 men. Three of the patients were diagnosed with KHE at 4 months old and one of them at 3 months old. None of the patients received a pathologic diagnosis, all of the diagnoses were clinical and only cases 1 and 4 included histopathological diagnosis. Only one of the patients had comorbidity: West Syndrome treated with vigabatrin, apparently not related to the main diagnosis. Two of the tumors were located in the lower left limb, one in the right costal region and another one in the right axillary region (Table 1). All patients were catheterized via right femoral artery with a 4-Fr introducer, C1 4-Fr catheters for main vessel navigation and Boston 0.21-Fr Direxion microcatheters for selective canulation and embolization of tumor´s feeding vessels (Supplemental Digital Content,

Table 1. - Clinical and Anatomical Characteristics of Patients Diagnosed With Kaposiform Hemangioendothelioma and Kasabach–Merritt Phenomenon
Patient Age*, mo Sex Comorbidities Tumor Localization
1 4 Male West Syndrome Right costal region
2 3 Male None Medial region of left quadriceps
3 4 Female None Medial region of left thigh
4 4 Male None Right axillary region
*Refers to the age at the moment of first transarterial embolization.

Case 1

A 4-month-old male patient was diagnosed with KHE in the right costal region which expanded all the way to the right abdominal flank, and the patient presented with the mass since birth (Figure 1). In his first admission, he presented with KMP demonstrated by anemia with serum hemoglobin of 6.7 g/dL and thrombocytopenia with 17 000 platelets/µL, at this point the patient had only received conservative treatment with vitamin K, platelet, and blood transfusions. Vitamin K was suspended 5 days previously to the first arteriography, a total of 24 days elapsed between diagnosis and first intervention. Arteriography was performed in which a vascular tumor in the right hemithorax was observed (Figure 1). This tumor received irrigation from the right axillary artery and the distal portion of the right mammary artery. An approximate reduction of more than 90% of blood supply was achieved after embolization of these arteries. After the first embolization, a chemotherapy regimen with vincristine and steroids was initiated. A couple of days after the first procedure the tumor clinically showed a size reduction as well as site induration. Based on the Society of Interventional Radiology (SIR) adverse event scoring included in Table 3, this patient was classified into category A: no therapy needed and no consequences after the invervention. Nevertheless, the patient persisted with severe thrombocytopenia of 13 000 platelets/µL and hemoglobin of 9.2 g/dL and showed signs of hemorrhage in pulmonary and gastrointestinal organ systems. A second embolization was performed in three irrigating intercostal arteries with hydrogel microspheres of 250–300 µm. Forty-eight hours after the procedure, a temporary increase in the platelet count was observed with a total of 20 000 per µL. Considering the lack of improvement due to persistent signs of consumption coagulopathy approximately 2 months after the first embolization, a total tumor resection was done as well as a resection of costal segments of 8th and 10th rib with a significant improvement in the platelet count at 48 hours after surgery of 239 000 per µL. There was no relapse of the tumor since diagnosis up until 6 months after the resection, and the chest wall remained stable with no wound or ventilatory complications. Follow-up on laboratory results is shown in Table 2.

Table 2. - Serum Hemoglobin and Platelets’ Patient Follow-up After Transarterial Embolization
Case 1 2 3 4
Number of Completed Procedures 2 Embolizations and 1 Resection 2 Embolizations 1 Embolization 1 Embolization
g/dL Hb in admission 04/03/19: 7 12/03/19: 8.8 24/05/19: 7.3 19/02/19: 8.8
Hb after 48 h 10/06/19: 7.9 15/05/19: 11.1 29/05/19: 6.2 24/02/19: 6.8
Hb after 1 wk 18/06/19: 13.1 No record. 14/06/19: 11.4 28/02/19: 11.5
Hb after 1 mo 17/08/19: 13.8 12/06/19: 12.4 11/07/19: 9.2 13/03/19: 10.2
Hb after 3 mo 30/09/19: 13 08/08/19: 13 20/08/19: 9.1 No record.
Hb after 6 mo No record* 01/11/19: 13.6 04/12/19: 10.5 No record*
plat/µL Plat. in admission 04/03/19: 15 000 12/03/19: 10 000 24/05/19: 23 000 19/02/19: 7 000
Plat. after 48 h 10/06/19: 239 000 15/05/19: 131 000 29/05/19: 49 000 24/02/19: 128 000
Plat. after 1 wk 18/06/19: 572 000 No record. 14/06/19: 25 000 28/02/19: 220 000
Plat. after 1 mo 17/08/19: 340 000 12/06/19: 311 000 11/07/19: 99 000 13/03/19: 673 000
Plat. after 3 mos 30/09/19: 541 000 08/08/19: 369 000 20/08/19: 51 000 No record
Plat. after 6 mo No record* 01/11/19: 292 000 04/12/19: 314 000 No record*
Dates are in DD/MM/YY format.
The first hospital admission laboratory results were taken into account and for 48 hours, 1 week, 1 month, 3 months, and 6 months follow-up the laboratory results after the last intervention were registered.
Abbreviations: Hb, hemoglobin; Plat., platelets.
*There is no laboratory record of this patient after 1 month of the last intervention due to treatment abandonment.

Table 3. - Society of Interventional Radiology Adverse Event Scoring
Category/Class Definition
Minor complications
A No therapy, no consequences
B Nominal therapy, no consequence; includes overnight admission for observation only
Major complications
C Requires therapy, minor hospitalization (<48 h)
D Requires major therapy, unplanned increase in level of care, prolonged hospitalization (>48 h)
E Permanent adverse sequelae
F Death

Figure 1.:
Case 1 embolization. A, First diagnostic arteriography in patient 1. B, Blood supply reduction in the majority of tumoral area in the first transarterial embolization. C, An erythematous lesion can be observed in right costal region that although it did not protrude it has a wide diameter. D, Tumor after 2 embolizations and previous to total resection. A site induration can be observed but there is a reduction in the diameter.

Case 2

A 3-month-old male patient diagnosed with KHE tumor in the right inguinal region. Upon admission, the patient had serum hemoglobin of 8.8 g/dL and 10 000 platelets/µL consistent with KMP. Due to high risk of hemorrhage, an arteriography was performed detecting a highly vascularized tumor (Figure 2) with feeding arteries from common, superficial and deep femoral artery as well as hypogastric artery. More than 80% of blood supply reduction was achieved after embolization with hydrogel microspheres. Forty-eight hours after the procedure, the patient had 81 000 platelets/µL and hemoglobin of 10.1 g/dL. One week after the intervention, a chemotherapy regimen of 4 cycles with intravenous vincristine (weekly dose of 0.3 mg) was initiated as well as treatment with prednisolone. A platelet count drop of 7000 platelets/µL was reported 1 week after the first chemotherapy cycle and 1 month after the procedure (after the third cycle) laboratory results with a serum hemoglobin of 9.6 g/dL and 11 000 platelets/µL were reported. The persistence of KMP accompanied by petechiae and hyperkeratosis on the tumor site as well as weak femoral artery pulses led to the performance of a second arteriography. Embolization of superficial and deep femoral arteries and popliteal artery was performed achieving a 60% of blood supply reduction. This patient showed no major complications due to the procedure, thus classified as an A based on SIR adverse event scoring. Forty-eight hours after the second intervention, an increase in hemoglobin was shown with a total of 11.1 g/dL and 131 000 platelets/µL. Six months after the last embolization, a full remission of the KMP was demonstrated by hemoglobin of 13.6 g/dL and 292 000 platelets/µL (Table 2). There was also a clinical remission of the tumor shown by full involution and skin induration of the same region.

Figure 2.:
Case 2 embolization. In the upper images, a significant blood supply reduction can be observed comparing (A) with respect to (B). In the lower images, a major clinical improvement can be observed due to a complete tumor remission in size an induration as well as redness decrease.

Case 3

A 4-month-old female patient was diagnosed with KHE tumor in the internal left thigh region accompanied by petechiae. Upon her first admission, she had 6.5 g/dL serum hemoglobin and 11 000 platelets/µL. She was first approached by general surgery and received medical therapy with propranolol and corticosteroids showing mild reduction of the site redness and petechiae after a few weeks of pharmacological management. The patient also showed an improvement in her serum hemoglobin with a total of 15.6 g/dL and 349 000 platelets/µL. Upon lack of clinical improvement, a chemotherapeutic regimen of 4 cycles with vincristine was initiated but the last cycle could not be completed due to treatment abandonment. She was readmitted due to an increase in tumor size with anemia and thrombocytopenia with 7.2 g/dL of hemoglobin and 23 000 platelets/µL, respectively. An arteriography was conducted observing a highly vascularized tumor with blood supply from the superficial and deep left femoral arteries. A 60 to 70% blood supply reduction was achieved after an embolization with 250 µm hydrogel microspheres. The patient developed cyanosis, local hypothermia, and center site ulceration as a local immediate complication, therefore classified as a B based on the SIR adverse event scoring. Forty-eight hours after the first embolization, a decrease in hemoglobin was reported with a total of 6.2 g/dL and an increase in platelet count with a total of 49 000 per µL, also showing mild improvement of site ulceration (Table 2). Follow-up after 6 months demonstrated a remission of KMP as well as tumor regression and ulcer healing, only left with mild site fibrosis and induration (Figure 3).

Figure 3.:
Case 3 embolization. A, Diagnostic arteriography shows a hypervascularized tumor with flow supply from profound and superficial femoral arteries. B, A significant blood flow reduction after embolization can be observed regarding (A). C, There is a clear compromise of full left leg adduction due to protruding tumoral mass. D–F, A gradual reduction of tumoral size, redness, as well as complete cicatrization of central ulceration.

Case 4

A 4-month-old male patient with KHE tumor in the right axillary region associated with KMP demonstrated by 8.8 g/dL hemoglobin and 7000 platelets/µL. Initially, the patient received propranolol and prednisolone without improvement; therefore, an arteriography was performed. The tumor feeding arteries were the right axillary artery and right mammary artery (Figure 4); after an embolization, there was a blood supply reduction of 100%. During the intervention, an apparent vasospasm was reported. Forty-eight hours after the procedure, the patient had persistent anemia with serum hemoglobin of 6.8 g/dL with no thrombocytopenia. Clinically, the patient developed apparent ischemia of the distal phalanges in the right hand with weak ulnar and radial pulses shown by the Doppler device. Twenty days after the procedure, there was a tumoral regression; nevertheless, the patient developed cyanosis and edema in the right superior extremity with progression to necrosis in distal phalanges. These complications belong to an E in the SIR adverse scoring system, with possible permanent sequelae that do not compromise his life. This patient could not be followed up due to treatment withdrawal and lack of follow-up; however, his last laboratory results, 1 month after the invasive treatment, reported 10.5 g/dL hemoglobin and a thrombocytosis of 679 000 platelets/µL (Table 2).

Figure 4.:
Case 4 embolization. A, A diagnostic arteriography with branches from feeding arteries to the tumoral site. B, Blood supply reduction in main arteries and its branches after transarterial embolization. Clinically, the tumor in (C) shows redness and a mass that limited full axilar adduction with size reduction and redness decrease after 1 month of embolization follow-up in (D).


The KHE was differentiated from infantile hemangioma for the first time in the year 1993 due to its invasive macroscopic characteristics as well as its similarities with Kaposi focal sarcoma that are definitively absent in infantile hemangioma.3 KHE has been well associated with the KMP that is defined by consumptive coagulopathy with thrombocytopenia and anemia. The KHE has a peak of presentation in the first year of life, and it has been observed that there is an increased prevalence in male patients.3 Up to 2013 according to the Consensus Pediatric Standards, there had been no standard of pharmacological treatment due to the lack of prospective studies.11 Several previous case series have reported significant improvement with corticosteroids and chemotherapy regimens with vincristine in patients with KHE with a success of 70.5%.12 Sirolimus is also recommended as a first-line treatment in patients with KHE with a success of 90.9% in the absence of KMP.12 However, when the patient presents KHE accompanied by KMP, the remission has not been clearly documented due to lack of established follow-ups or clinical trials.3,12,13 Other authors have presented cases treated with transarterial embolization showing improvement in the platelet count.14,15 Coadjuvant treatments with tranexamic acid, platelet transfusion, blood transfusion, and fibrinogen reposition have been reported; however, this therapy is only used to improve some parameters at the moment of KMP diagnosis and to reduce risk of hemorrhage complications with no resolution of the actual problem.5

Previous case series have mentioned the possibility of invasive procedures such as total tumor resection, although is not the best option of treatment since patients with KMP present high risk of hemorrhage, in addition, these tumors are difficult to completely resect due to its infiltrative properties and the risk of long-term morbidity after these surgeries is high. Other studies have considered transarterial embolization of feeding tumor arteries but consider it a high-risk intervention due to their small size taking into account the patients’ age and weight and the possible complications that could follow after the procedure such as embolization of the total feeding artery as well as compromise of vital structures or ischemia of other structures that surround the tumor. Since the transarterial embolization is operator-dependent as any other surgical open or microinvasive procedure few cases have been reported of patients who have been treated with transarterial embolization for this specific diagnosis. In 2012, García Monaco reported a case series of 2 patients with KHE who were successfully treated with transarterial embolization and vincristine.14 This study demonstrates with a series of 4 cases (Table 4) that transarterial embolization is an intervention that offers significant clinical improvement and, most importantly, a significant reduction of hemorrhage risk due to the immediate cessation of blood tumoral flow that stops platelet and red blood cells as well as other blood clotting factors such as fibrinogen. One patient in these series of 4 cases showed complete tumoral remission only after resection, but in the meantime, he showed immediate and temporary improvement of platelet and hemoglobin counts as well as clinical tumor reduction after transarterial embolization. We have to state that this patient was not receiving adequate medical treatment, so the embolization worked as a stabilization procedure of the KMP. The last case involved a patient that unfortunately could not be followed up, their parents abandoned consult follow-up. Whether this patient lost his distal phalanges due to necrosis or not is uncertain (cannot really be known). It is important that complications such as main arterial obstruction with hydrogel microspheres most of the times can be avoided, but we have to remember that vascular tumors usually have extra anastomoses, which sometimes cannot be seen in the arteriography and can end up with nontarget embolization. (It is important to emphasize that these procedures require operator ability to avoid future complications.) In our center embolization in pediatric patients’ program started in March 2017, with a usual basis of 50 procedures per year average, since then, only 2 patients (one included in these report) had nontarget embolization as a complication.

Table 4. - Medical and Invasive Treatment Overall Outcome
Case Number Chemotherapy Agent Number of Embolization Procedures Surgical Procedures Overall Outcome
1 VCR weekly 2 1 KMP remission, no MAE
2 VCR weekly 2 0 KMP remission, no MAE
3 VCR weekly 1 0 KMP remission, no MAE
4 VCR weekly 1 0 KMP remission, digital ischemia no amputation
Abbreviations: MAE, major adverse events; VCR, vincristine.


Transarterial embolization of feeding arteries is not a novel management proposal for KHE; however, few physicians perform it as a curative treatment for KHE. The correct diagnosis of this life-threatening vascular tumor gives an opportunity for these patients to receive the correct pharmacological and endovascular approach, therefore reducing the mortality rate. Transarterial embolization with hydrogel microspheres shows promising results as an adjunctive therapy, in patients with clinical diagnosis of KHE and KMP where medical treatment demonstrates slow or no response of improving KMP. More is yet to know about this rare vascular tumor; nonetheless, transarterial embolization offers encouraging results in a usually nonremitting diagnosis.


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Kaposiform hemangioendothelioma; Kasabach–Merritt phenomenon

Supplemental Digital Content

Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The International Society for the Study of Vascular Anomalies.