Kaposi's Sarcoma - Pathology and Diagnosis

Pathology and Diagnosis

Despite its name, in general it is not considered a true sarcoma, which is a tumor arising from mesenchymal tissue. KS, in fact, arises as a cancer of lymphatic endothelium and forms vascular channels that fill with blood cells, giving the tumor its characteristic bruise-like appearance. KSHV proteins are uniformly detected in KS cancer cells.

KS lesions contain tumor cells with a characteristic abnormal elongated shape, called spindle cells. The tumor is highly vascular, containing abnormally dense and irregular blood vessels, which leak red blood cells into the surrounding tissue and give the tumor its dark color. Inflammation around the tumor may produce swelling and pain.

Although KS may be suspected from the appearance of lesions and the patient's risk factors, definite diagnosis can be made only by biopsy and microscopic examination, which will show the presence of spindle cells. Detection of the KSHV protein LANA in tumor cells confirms the diagnosis.