Retiform hemangioendothelioma. A new case in a child with diffuse endovascular papillary endothelial proliferation.

We present a new case of retiform hemangioendothelioma (RH), an entity first described by Calonje et al. in 1994. The tumor was intradermal and located on the toe of an 11-year-old boy. Histologically, in addition to the distinctive retiform pattern of proliferating vessels in RH there are intraluminal papillae with hyaline cores similar to those seen in malignant endovascular papillary angioendothelioma (Dabska's tumor), but usually they are infrequent, focal and poorly developed. In our case, these papillary structures were well formed and distributed in a diffuse way. They were most conspicuous in superficial areas where the blood vessels were dilated. In deep areas, where the pattern of neoplastic vessels was retiform, the papillae filled their lumina totally, resembling solid cords. Our case shares the clinical and morphologic features of both retiform hemangioendothelioma and Dabska's tumor, supporting a relationship between these two kinds of neoplasms. The benign behavior of this case, with no recurrence or metastases over a 4-year follow-up, corresponds to the low malignancy of this kind of vascular neoplasm.