Intravascular Kaposi's sarcoma - a hitherto unrecognized phenomenon

Based on the spectrum of histological features, Kaposi's sarcoma (KS) is grouped into patch, plaque and nodular stages. The histological changes overlap, especially with lesional evolution. To date, intravascular KS is undocumented.

A clinicopathological description of six cases of intravascular KS.

Clinical: There were four men and two women (mean age = 65 years). Four patients, who presented clinically with classic (sporadic) KS, developed solitary violaceous nodules on the extremities. Two patients with acquired immune deficiency syndrome-related KS had disseminated cutaneous KS lesions in all stages of evolution. Six months to 3 years follow-up showed no evidence of systemic KS in any of the patients. Histopathology: Exclusive intravascular growth was seen in five patients. The vascular channels, highlighted by mural immunostaining with desmin and anti-smooth muscle actin, had the histological features of veins. Intravascular growth was characterized by interlacing fascicles of human herpesvirus 8, CD31 and CD34-positive spindle cells with formation of cleft-like spaces, erythrocyte extravasation, hyaline globules and a lymphoplasmacytic infiltrate. One patient had a proliferation of irregular, vascular channels in the desmin in addition to the intravenous growth.

Intravascular KS is a peculiar hitherto unrecognized morphological variant of KS that does not seem to be associated with an increased risk of aggressive behaviour.