[Epithelioid hemangioendothelioma of the soft tissue. Histology and ultrastructural cytology].

Described in this paper is a case of epithelioid haemangioendothelioma of soft tissue localised in the subcutis of the upper arm of a 47-year old man. The tumour was histologically characterized by cords and nests of plump epithelioid cells separated from each other by typical myxohyaline stroma. Light microscopy revealed also definite vasoformative areas and solid regions with vacuolization which were indicative of so-called intracytoplasmic vacuoles. Atypical nuclei were conspicuous findings. Ultrastructural and immunohistochemical investigations demonstrated the endothelial origin of the lesion. Immunohistochemical investigations also revealed the presence of cellular areas which produced positive response to "factor-VIII-associated antigen". Ultrastructurally the tumour cells exhibited densely packed microfilaments, 8 nm to 10 nm in thickness, and intracytoplasmic vacuoles. The latter were lined and delimited by single membranes, and some of these exhibiting luminal microvilli. The tumour cells exhibited typical pinocytotic vacuoles, with the cords or nests being encircled by thin basal membranes. Typical Weibel-Palade bodies were detectable in some cells. Also recordable from certain cells were intracytoplasmic crystalloid inclusion bodies of a kind never described before in the context of tumour cells of epithelioid haemangioendothelioma. Those inclusions were composed of substructural units of parallel electrodense lines, 19nm to 21nm in periodicity. The nature of epithelioid haemangioendothelioma and its relations with intravascular bronchiolo-alveolar tumours (IVBAT) and myxoid angioblastomatosis of bone were discussed in some detail.