Pediatric Hepatic Vascular Tumors: Clinicopathologic Characteristics of 33 Cases and Proposed Updates to Current Classification Schemes

Pediatric hepatic vascular tumors (HVT) are rare neoplasms with features distinct from their cutaneous counterparts. Behavior ranges from benign to malignant with each subtype having therapeutic differences. Histopathologic descriptions of large cohorts are scarce in the literature. 33 putative HVTs diagnosed from 1970 to 2021 were retrieved. All available clinical and pathologic material was reviewed. Lesions were reclassified according to the World Health Organization (WHO) classification of pediatric tumors [1] as: hepatic congenital hemangioma (HCH; n=13), hepatic infantile hemangioma (HIH; n=10), hepatic angiosarcoma (HA; n=3), and hepatic epithelioid hemangioendothelioma (HEH; n=1). Vascular malformations (n=5) or vascular dominant mesenchymal hamartoma (n=1) were excluded. HCH frequently showed involutional changes while HIH often had anastomosing channels and pseudopapillae formation. HA had solid areas with epithelioid and/or spindled endothelial morphology, significant atypia, increased mitoses, high proliferation index, and occasionally necrosis. On morphology, a subset of HIH showed features worrisome for progression to HA including solid “glomeruloid” proliferation, increased mitoses, and epithelioid morphology. The widely metastatic and fatal HEH was in a 5-year-old male with multiple liver lesions. Immunohistochemically, HIHs and HA were GLUT-1 positive. 1 HIH patient died from post-operative complications, while 3 are alive without disease. 5 HCH patients are alive and well. 2/3 HA patients died of disease and 1/3 is alive without recurrence. To our knowledge, this is the largest series of pediatric HVTs reviewing clinicopathologic features based on current Pediatric WHO nomenclature [1]. We highlight diagnostic challenges and propose inclusion of an intermediate category between HIH and HA which warrants closer follow-up.