Hemangioendothelioma is a rare vasoformative lesion of intermediate biologic behavior.
4,5) It is important for the surgical pathologist to recognize this rare benign vascular proliferation and differentiate it from other vasoformative lesions involving splenic parenchyma, particularly tumors of intermediate malignant potential, such as hemangioendothelioma and the highly aggressive angiosarcoma.
These tumors can have focal vasoformative
areas, vimentin and cytokeratin positivity, CD34 positivity (-50%), (14) intracytoplasmic vacuolization, focal areas of necrosis, and a variable degree of mitotic activity, giving the impression of epithelioid angiosarcoma.
They suggest that in VPTR, the significant proliferative activity is astrocytic and that, presumably, the vascular component is secondary to the release of vasoformative
factors by the glial cells.
Large, clear intracytoplasmic vacuoles are usually present; however, the vasoformative
potential of these cells is most often realized as well-formed vessels arranged in lobules.
lumens sometimes contained fragmented red blood cell by-products that were densely basophilic on Papanicolaou and on Diff-Quik stains (Figure 3).
The key to diagnosis is recognition of atypical vasoformative
spindled and epithelioid cells distributed in a distinctly lymphangitic pattern.
However, the lack of demonstrable mucin in the vacuoles and the presence of erythrocytes in some vacuoles indicate that these are vasoformative
vacuoles rather than mucin vacuoles.
4] Microscopic examination reveals malignant cells invading liver parenchyma and vasoformative
areas with vessels lined by malignant endothelial cells.
13] Ohsawa et al suggest that the combination of endothelial cell markers, including factor VIII, UEA-1, and CD31, is useful in the diagnosis of angiosarcoma, particularly with a nonvasoformative or poorly vasoformative
They were composed of conventional vasoformative
areas admixed with poorly differentiated sheets of both spindle cells and epithelioid cells (Figure 2, A).
Benign hemangioendothelioma-like foci with compressed lumens are detected focally; however, there is no evidence of active endothelial proliferation, florid papillations, or cellular atypia in the context of a borderline or malignant vasoformative
neoplastic process (Figure 2, E and F).