Tumours of lymphatic vessels of the skin and soft tissues

Tumours of lymphatic vessels comprise only a small group in the heterogeneous spectrum of vascular neoplasms of skin and soft tissues. However, this discrepancy between haemangiomas/angiosarcomas and lymphangiomas/lymphangiosarcomas probably represents the present inability to reliably differentiate between lymphatic and capillary vascular endothelium. Histologically, neoplastic lymphatic vessels tend to be lined by endothelial cells with plumper and more prominent, matchstick-like nuclei (in contrast to vascular spaces in haemangiomas that are lined by flat or epithelioid endothelial cells), often show variations in the thickness of the vessel walls and are not completely surrounded by actin-positive (myo)pericytes. Endothelial cells in lymphatic neoplasms tend to be negative for CD34 or stain only focally positive for this marker and an expression of lymphatic markers as vascular endothelial growth factor-C receptor (VEGFR-3), podoplanin and M2A oncofetal antigen has been reported most recently. In addition to "traditional" lymphatic neoplasms including lymphangioma circumscriptum, cavernous lymphangioma/cystic hygroma, benign lymphangioendothelioma, lymphangiomatosis and the rare lymphangiosarcoma, histological and immunohistochemical features of a group of vascular neoplasms with a hobnail cytomorphology (hobnail haemangioma, retiform haemangioendothelioma, papillary intralymphatic angioendothelioma, benign lymphangiomatous papule following radiotherapy) suggest that these lesions also belong to the spectrum of tumours of lymphatic vessels.