Kaposi's sarcoma-Human herpesvirus 8-associated

A low-power view shows this vascular tumor infiltrating along bronchovascular bundles (upper left), and growing as isolated nodules (arrow points to one). Tumor may be very vascular or less so, as seen below.

Kaposi's sarcoma--cellular focus

At higher magnification, multiple small, irregular-sized vascular channels are formed by spindled tumor cells with irregular, hyperchromatic nuclei. Scattered inflammatory cells and extravasated RBCs are present.

Kaposi's sarcoma--endobronchial biopsy

Small biopsy specimens are diagnostic when atypical cells, small, irregular vascular channels, extravasated RBCs, and hemosiderin pigment are present. The diagnosis is strengthened by typical bronchoscopic findings and the presence of confirmed extrapulmonary Kaposi's sarcoma.