Polymorphous hemangioendothelioma: a report of two cases, one affecting extranodal soft tissues, and review of the literature.

Polymorphous hemangioendothelioma (PH) is a rare vascular neoplasm occurring in lymph nodes. It has been considered a borderline malignant tumor, mainly because of a local recurrence in one of the three cases described to date. This report adds two additional cases, one in which the tumor was extranodal. An extensive immunohistochemical study and thorough literature review were undertaken. The patients, a 55-year-old man and a 28-year-old man, both asymptomatic, presented with tumors involving a left pulmonary hilar lymph node (3 cm) and the soft tissues of the left paravertebral region (4 cm), respectively. The tumors were composed of an admixture of solid, primitive vascular and ectatic angiomatous components, with both elements formed by uniform, polygonal cells. In one case, the cells marked for CD31 and factor VIII, and the other case was positive for CD34. Neither case marked for epithelial membrane antigen and keratin. One tumor partially replaced a lymph node, and no nodal tissue was identified in the other. Of the three previously reported cases of nodal PH, one had recurring and metastatic behavior. PH is a rare, malignant vascular neoplasm that most frequently involves lymph nodes, but it can also affect extranodal locations.