Kaposiform haemangioendothelioma: a review with emphasis on histological differential diagnosis

Forty-nine specimens from a variety of vascular lesions were analyzed for cellular characteristics. Two major categories of lesions emerged from this investigation: hemangiomas and vascular malformations. This classification and its implications are justified by several considerations. Hemangiomas in the proliferating phase (n = 14) were distinguished by (1) endothelial hyperplasia with incorporation of [3H]thymidine, (2) multilaminated basement membrane formation beneath the endothelium, and (3) clinical history of rapid growth during early infancy. Hemangiomas in the involuting phase (n = 12) exhibited (1) histologic fibrosis and fat deposition, (2) low to absent [3H]thymidine labeling of endothelial cells, and (3) rapid growth and subsequent regression. The endothelium in hemangiomas had many characteristics of differentiation: Weibel-Palade bodies, alkaline phosphatase, and factor VIII production. Vascular malformations (n = 23) demonstrated no tritiated thymidine incorporation and normal ultrastructural characteristics. These lesions were usually noted at birth, grew proportionately with the child, and consisted of abnormal, often combined, capillary, arterial, venous, and lymphatic vascular elements. This cell-oriented analysis provides a simple yet comprehensive classification of vascular lesions of infancy and childhood and serves as a guide for diagnosis, management, and further research.

Vascular anomalies represent a spectrum of disorders from a simple "birthmark" to life- threatening entities. Incorrect nomenclature and misdiagnoses are commonly experienced by patients with these anomalies. Accurate diagnosis is crucial for appropriate evaluation and management, often requiring multidisciplinary specialists. Classification schemes provide a consistent terminology and serve as a guide for pathologists, clinicians, and researchers. One of the goals of the International Society for the Study of Vascular Anomalies (ISSVA) is to achieve a uniform classification. The last classification (1997) stratified vascular lesions into vascular malformations and proliferative vascular lesions (tumors). However, additional disease entities have since been identified that are complex and less easily classified by generic headings, such as capillary malformation, venous malformation, lymphatic malformation, etc. We hereby present the updated official ISSVA classification of vascular anomalies. The general biological scheme of the classification is retained. The section on tumors has been expanded and lists the main recognized vascular tumors, classified as benign, locally aggressive or borderline, and malignant. A list of well-defined diseases is included under each generic heading in the "Simple Vascular Malformations" section. A short definition is added for eponyms. Two new sections were created: one dealing with the malformations of individually named vessels (previously referred to as "truncular" malformations); the second groups lesions of uncertain or debated nature (tumor versus malformation). The known genetic defects underlying vascular anomalies are included in an appendix. This classification is meant to be a framework, acknowledging that it will require modification as new scientific information becomes available.

Complicated vascular anomalies have limited therapeutic options and cause significant morbidity and mortality. This Phase II trial enrolled patients with complicated vascular anomalies to determine the efficacy and safety of treatment with sirolimus for 12 courses; each course was defined as 28 days.