This lesion was removed from the abdomen of a 23-year-old pregnant woman. Microvenular hemangiomas are uncommon, but appear more often in pregnant women, as in our case, suggesting a hormonal role in their histogenesis. The histology in this case is typical, with small-vessel proliferation within a sclerotic stroma. The differential diagnosis may include Kaposi sarcoma, but those lesions often show more cytologic atypia and poor vessel formation.
At higher power, the lesion consists of endothelial cell proliferation, 1-2 cell layers thick. The vessels are small, open, and thin-walled, corresponding to microvenules. The intervening stroma contains thickened sclerotic collagen bundles. No cytologic atypia is appreciated.