Cellular variant of kaposiform lymphangiomatosis: a report of three cases, expanding the morphologic and molecular genetic spectrum of this rare entity.

Kaposiform lymphangiomatosis (KLA) is a very rare form of generalized lymphatic anomaly, consisting of a diffuse proliferation of abnormal, dilated lymphatics, and small fascicles of hemosiderin-laden spindled lymphatic endothelial cells. KLA occurs in children and young adults and may present with multicentric disease, pleural and pericardial effusions, and life-threatening coagulopathy. Genetically, KLA most often harbors somatic activating mutations in NRAS. We recently encountered 3 cases of KLA with cellular features, resembling kaposiform hemangioendothelioma (KHE), and studied their clinicopathologic, radiologic, and molecular genetic features. The patients (1 male, 2 females; aged 2 years, 2 months, 4 years) presented with multicentric disease involving skin, soft tissue, bone, and spleen and thrombocytopenia/coagulopathy. Advanced imaging studies confirmed multicentric disease. Biopsies (skin, soft tissue, bone, and spleen) demonstrated both conventional KLA and much more cellular foci, consisting of sheets, nodules, glomeruloid structures, and sieve-like arrays of lymphatic endothelial cells (positive for CD31 and D2-40). Cellular areas superficially resembled KHE but displayed more epithelioid cytology and lacked surrounding hyaline fibrosis and minute platelet aggregates. Molecular genetic studies demonstrated NRAS c.181C > A p.Q61K (Gln61Lys) in 2 specimens from one patient and HRAS p.A59_Q61delinsGGSIL in another. Two patients were treated with sirolimus; all are currently alive with stable disease. We conclude that cellular morphology in KLA, a previously undescribed feature, does not appear to be associated with clinical features, site of disease, mutation type, response to sirolimus, or outcome. Although cellular KLA may mimic KHE, there are sufficient clinical, morphologic, and genetic differences such that these are likely unrelated diseases.

Kaposiform hemangioendothelioma further broadens the phenotype of PIK3CA-related overgrowth spectrum.

Kaposiform hemangioendothelioma (KHE) is a rare locally aggressive mixed vascular tumor, with typical onset in early childhood and characterized by progressive angio- and lymphangiogenesis. Its etiopathogenesis and molecular bases are still unclear. Here, we report the first case of congenital KHE harboring a PIK3CA mosaic pathogenic variant (c.323G > A, p.Arg108His) in a boy with very subtle PIK3CA-related overgrowth spectrum (PROS) features. This finding provides insights into the pathophysiology of KHE, offering targeted therapeutic options by inhibition of the PI3K/Akt/mTOR pathway. We propose the inclusion of this mixed lymphatic and vascular anomaly within the PROS.

Diffuse bone and soft tissue angiomatosis with GNAQ mutation.

We describe a unique case of skeletal and extraskeletal angiomatosis complicated by Kasabach-Merritt syndrome. The patient was a 3-year-old boy, who presented with involvement of both femurs and left tibia, as well as with soft tissue lesions of the left thigh. At birth, multiple hemangiomas of the soft tissues of the frontal and parietal scalp had been identified, together with a space-occupying lesion of the lung. Histologically, the skeletal and soft tissue lesions consisted of a proliferation of thin-walled, dilated blood vessels, with an endothelial lining devoid of atypia and exhibiting immunoreactivity for CD31 and CD34, while podoplanin and GLUT1 were negative. Whole exome sequencing performed on samples from the lesion of the femur, the tibia and the skin of the thigh, showed a GNAQ (c.286A>T:p.T96S) variant in all specimens, that was confirmed with digital droplet PCR. This case expands the clinical and pathologic spectrum of vascular proliferations showing similar molecular biology, characterized by GNAQ, GNA11 or GNA14 mutations.

Kaposiform hemangioendothelioma and tufted angioma - (epi)genetic analysis including genome-wide methylation profiling.

Kaposiform hemangioendothelioma (KHE) is a locally aggressive vascular condition of childhood and is clinicopathologically related to tufted angioma (TA), a benign skin lesion. Due to their rarity molecular data are scarce. We investigated 7 KHE and 3 TA by comprehensive mutational analysis and genome-wide methylation profiling and compared the clustering, also with vascular malformations. Lesions were from 7 females and 3 males. The age range was 2 months to 9 years with a median of 10 months. KHEs arose in the soft tissue of the thigh (n = 2), retroperitoneum (n = 1), thoracal/abdominal (n = 1), supraclavicular (n = 1) and neck (n = 1). One patient presented with multiple lesions without further information. Two patients developed a Kasabach-Merritt phenomenon. TAs originated in the skin of the shoulder (n = 2) and nose/forehead (n = 1). Of the 5 KHEs and 2 TAs investigated by DNA sequencing, one TA showed a hot spot mutation in NRAS, and one KHE a mutation in RAD50. Unsupervised hierarchical clustering analysis indicated a common methylation pattern of KHEs and TAs, which separated from the homogeneous methylation pattern of vascular malformations. In conclusion, methylation profiling provides further evidence for KHEs and TAs potentially forming a spectrum of one entity. Using next generation sequencing, heterogeneous mutations were found in a subset of cases (2/7) without the presence of GNA14 mutations, previously reported in KHE and TA.

What is new in endothelial neoplasia?

The classification of vascular neoplasms continues to evolve as we accumulate more genetic and clinical data, particularly for rare tumor types. Because of tumor rarity, changes to classification schema, overlapping histologic features, and in some cases, lack of morphologic evidence of vasoformation, vascular neoplasms present a diagnostic challenge. Here, we discuss recent developments in our understanding of vascular tumors, with a detailed discussion of epithelioid hemangioma, tufted angioma, kaposiform hemangioendothelioma, composite hemangioendothelioma, pseudomyogenic hemangioendothelioma, epithelioid hemangioendothelioma, and angiosarcoma.

Tufted angioma with associated Kasabach-Merritt phenomenon caused by somatic mutation in GNA14.

Tufted angioma (TA) is a rare vascular tumor characterized by histologic tufts of proliferating capillaries that occurs in infancy or early childhood, with a poorly understood pathogenesis. Though benign, TA can be associated with the Kasabach-Merritt phenomenon (KMP), a life-threatening consumptive coagulopathy and thrombocytopenia. Here, we explored the genetic mechanism underlying a case of TA associated with KMP via targeted sequencing of laser capture micro-dissected lesion and blood DNA, and identified a somatic, activating GNA14 mutation specific to the tumor. Our findings support aberrant GNA14 activation underlies the pathogenesis of TA associated with KMP.

Activation of Hedgehog Signaling in Aggressive Hepatic Hemangioma in Newborns and Infants.

BACKGROUND/AIM: Hepatic hemangiomas (HH) can show an aggressive course with significant complications. Prognostic markers that identify an aggressive course are entirely absent. Since we have showed that Hedgehog signaling is overexpressed in aggressive hemangiomas of the skin. Here, we hypothesize that it is also altered in aggressive HH. MATERIALS AND METHODS: Immunohistological staining for GLUT1 and quantitative PCR was performed in seven specimens with aggressive HH. For comparison, we included specimens of kaposiform hemangioendothelioma (KHE), skin hemangioma and normal liver tissue. RESULTS: Overexpression of the Hedgehog signaling components SHH and GLI2 and its target gene FOXA2 in HH were similar to those found in aggressive skin hemangioma and KHE, their expression being significantly higher than in mild skin hemangioma. High expression levels of SHH and FOXA2 positively correlated with HH, but not with normal liver tissue. CONCLUSION: Hedgehog signaling is up-regulated in aggressive HH. This finding may lead to a biomarker allowing early intervention.

[Role of master transcriptional factor Prox-1 in lymphatic endothelial differentiation of Kaposiform hemangioendothelioma].

Objective: To analyze the clinical and pathological features of Kaposiform hemangioendothelioma (KHE), and to investigate the role of master transcriptional factor Prox-1 in the regulation of lymphatic differentiation. Methods: Nine cases of KHE (during the period from October 2009 to June 2016) were collected with clinical and pathological data. H&E stained section review and immunohistochemietry using the Dako EnVision method were performed. Results: There were 6 female and 3 male patients with age ranging from 2 months to 8 years (median 3 years and 4 months). The patients presented with either single subcutaneous soft tissue mass, or bone tumors, with the duration of disease onset ranging from 1 month to 1 year. The sites of involvement included the skins of neck (2 cases), nose root (1 case), inguinal (1 case), thigh root (1 case), humerus (2 cases), lumbar vertebrae(1 case), and mesentery (1 case). These tumors were histologically composed of nodules of densely packed spindle or ovoid cells and deformed small blood vessels in an invasive growth pattern. The tumor cells were immunohistochemically positive for both blood vessels and lymphatic endothelial markers, including Prox-1, the master transcriptional factor, and VEGFR-3. With followed-up from 1 to 60 months (median 26 months), two patients died of the disease, while the remaining patients were alive without recurrence. Conclusions: KHE is a rare vascular tumor with at least partial lymphatic endothelial differentiation, in which Prox-1 may act as a master regulator for such differentiation. KHE is an aggressive tumor of intermediate malignant potential, with local invasion and recurrence tendency, and long term follow-up is required.

Exome sequence analysis of Kaposiform hemangioendothelioma: identification of putative driver mutations

Abstract BACKGROUND: Kaposiform hemangioendothelioma is a rare, intermediate, malignant tumor. The tumor's etiology remains unknown and there are no specific treatments. OBJECTIVE: In this study, we performed exome sequencing using DNA from a Kaposiform hemangioendothelioma patient, and found putative candidates for the responsible mutations. METHOD: The genomic DNA for exome sequencing was obtained from the tumor tissue and matched normal tissue from the same individual. Exome sequencing was performed on HiSeq2000 sequencer platform. RESULTS: Among oncogenes, germline missense single nucleotide variants were observed in the TP53 and APC genes in both the tumor and normal tissue. As tumor-specific somatic mutations, we identified 81 candidate genes, including 4 nonsense changes, 68 missense changes and 9 insertions/deletions. The mutations in ITGB2, IL-32 and DIDO1 were included in them. CONCLUSION: This is a pilot study, and future analysis with more patients is needed to clarify: the detailed pathogenesis of this tumor, the novel diagnostic methods by detecting specific mutations, and the new therapeutic strategies targeting the mutation.

Exome sequence analysis of Kaposiform hemangioendothelioma: identification of putative driver mutations.

BACKGROUND:: Kaposiform hemangioendothelioma is a rare, intermediate, malignant tumor. The tumor's etiology remains unknown and there are no specific treatments. OBJECTIVE:: In this study, we performed exome sequencing using DNA from a Kaposiform hemangioendothelioma patient, and found putative candidates for the responsible mutations. METHOD:: The genomic DNA for exome sequencing was obtained from the tumor tissue and matched normal tissue from the same individual. Exome sequencing was performed on HiSeq2000 sequencer platform. RESULTS:: Among oncogenes, germline missense single nucleotide variants were observed in the TP53 and APC genes in both the tumor and normal tissue. As tumor-specific somatic mutations, we identified 81 candidate genes, including 4 nonsense changes, 68 missense changes and 9 insertions/deletions. The mutations in ITGB2, IL-32 and DIDO1 were included in them. CONCLUSION:: This is a pilot study, and future analysis with more patients is needed to clarify: the detailed pathogenesis of this tumor, the novel diagnostic methods by detecting specific mutations, and the new therapeutic strategies targeting the mutation.

Laryngomalacia and complicated, life-threatening mTOR-positive Kaposiform hemangioendothelioma cured by Supraglottoplasty and sirolimus.

The therapy of complicated Kaposiform hemangioendothelioma (KHE) is still difficult. We present the first case of laryngomalacia with simultaneous mammalian target of Rapamycin (mTOR)-positive KHE of the neck and thoracic inlet and concurrent Kasabach-Meritt Phenomenon (KMP) in an 11-month-old boy suffering life-threatening progress despite intravenous vincristine, corticosteroids, propranolol and local interstitial laser-application. The laryngomalacia restored after laser-supraglottoplasty. Successfully treatment of the prior fatal course of the KHE with KMP was initiated not till adding the mTOR inhibitor sirolimus to therapy. After 16 months single therapy of KHE with oral sirolimus the boy presented free of symptoms with minimal residual disease and excellent functional long-term results. Thus we stopped sirolimus therapy. The results are stable for 9 months without therapy. The special features including full report of histopathologic findings of this utmost complicated case are demonstrated in detail underlining the effectiveness of sirolimus for KHE.

Medical and genetic aspects of vascular anomalies.

This manuscript provides an updated review of clinical and scientific or genetic updates in vascular anomalies, with an emphasis on essential information for the interventional radiologist. Citations include concise reviews and reliable websites which provide supplementary background. This manuscript elucidates the following: (1) not every vascular lesion is a hemangioma, (2) the Kasabach-Merritt phenomenon is not seen in association with typical hemangiomas, (3) many new basic research and genetic findings in vascular anomalies may influence the clinical evaluation and diagnosis (as well as provide rationale for future targeted therapies which may successfully ameliorate or eradicate these conditions), (4) it is essential to communicate with the clinician and patient to understand the history, physical findings, and best approach to evaluation and management, and (5) multiple specialists are often involved, and multidisciplinary teams of physicians and ancillary healthcare workers often collaborate.