Benign lymphangioendothelioma develops as a solitary, slow-growing, variably erythematous patch or plaque which usually occurs on the extremities or trunk of adolescents or adults. Benign lymphangioendothelioma has also been called "acquired progressive lymphangioma" and "angioendothelioma". Microscopy shows thin walled endothelium-lined spaces within the superficial papillary dermis, but also occasionally extending throughout the dermis and rarely the subcutaneous tissue. In the superficial dermis the vascular spaces tend to run horizontally, while in the deep dermis the vascular spaces tend to dissect the collagen. The endothelial cells lining the vessels are more numerous than in normal lymphatics. However, there is no obvious nuclear atypia or malignant cytologic change. Hemosiderin deposition is minimal and the inflammatory cell infiltrate is sparse.
The reported cases of benign lymphangioendothelioma have been cured by local excision with no recurrence, progression or metastasis reported with this conservative treatment.
The differential diagnosis includes well differentiated angiosarcoma. In fact, the cases previously called "angioendothelioma" were thought to represent lesions of borderline malignancy. However, an angiosarcoma usually appears on the face and scalp of an elderly person, is multifocal in 50% of cases, and microscopically shows obvious cytologic atypia of the endothelial cells. The finding of mitoses favors angiosarcoma. Angiosarcoma may occasionally show moderately to poorly differentiated areas as a clue to the correct diagnosis.
In this case of a 26 year old female with a thigh lesion, Kaposi's sarcoma represented a difficult differential diagnosis. Clinically, both benign lymphangioendothelioma and Kaposi's sarcoma can present as slightly raised reddish plaques, but the benign lymphangioendothelioma is more often solitary and tends to grow more slowly than Kaposi's sarcoma. Classical Kaposi's sarcoma is more common in men (male to female ratio 10-15:1) and older individuals. Benign lymphangioendothelioma tends to occur in younger individuals with a more equal sex distribution.
Histologically the early "patch" stage of Kaposi's sarcoma can be difficult if not impossible to distinguish from benign lymphangioendothelioma. Early "patch" stage lesions are characterized by an increased number of dilated jagged, thin-walled spaces lined by thin endothelial cells throughout most of the dermis (especially the upper half). These thin walled spaces often surround venules of the normal vascular plexusb ( the so called "promontory sign"). The lesions of Kaposi's sarcoma tend to have a moderate infiltrate of lymphocytes and plasma cells around the newly formed vascular spaces. Extravasation of red blood cells and hemosiderin deposition can be seen, and in slightly more advanced cases an increase in spindle cells may be seen dissecting between collagen bundles in the dermis.
Immunohistochemistry is not helpful in distinguishing the two entities. Patch stage Kaposi's sarcoma is Ulex europaeus agglutinin 1(UEA-1) positive and Factor VIII RA negative. The same immunohistochemical profile has been reported with benign lymphangioendothelioma.
This 26 year-old female patient is apparently immunocompetent. The lesion has been static without treatment for at least two years. HIV serologic studies were twice negative. Thus, the clinicopathologic assessment is required for the diagnosis.
Contributed by Steven Ruhoy, MD and Kevin Flynn, MD