Kaposi's sarcoma.

Kaposi's sarcoma (KS) is a vascular tumor that commonly affects the head and neck, particularly in patients infected with human immunodeficiency virus (HIV). Human herpesvirus 8 (HHV8), shed mainly in saliva, is important in KS development. Mucocutaneous KS and lymph node involvement of the head and neck are often the presenting symptoms of acquired immunodeficiency syndrome (AIDS). In rare cases, KS affects the major salivary glands, either as a primary infiltrating neoplasm within the gland parenchyma or as intranodal involvement. Therefore, it is important to include KS in the differential diagnosis of AIDS-associated salivary gland enlargement.

The classic microscopic features of KS are intersecting compact, coalescing, and sheet-like fascicles of uniform, mildly atypical spindle cells that delineate either slit-like or sieve-like vascular spaces that contain extravasated erythrocytes (figure 1). Irregular vascular channels are lined with plump endothelial cells that contain nuclei of irregular size and shape. Mitotic figures, including atypical forms, are easily identified. The tumor nearly always contains characteristic intracellular and extracellular periodic-acid-Schiff-positive, diastase-resistant, glassyhyaline (eosinophilic) globules. Stromal hemosiderin deposition and inflammatory cells, particularly plasma cells, are often present. Immunohistochemical studies show that the spindle cells are positive for endothelial markers, such as factor VIII-related antigen, CD31, and CD34. The detection of HHV8 in KS spindle cells is a useful tool in distinguishing KS from its mimics (figure 2). Histologically, the differential diagnosis includes other vascular neoplasms, such as hemangiomas, angiosarcomas and, less commonly, spindle-cell myoepithelial neoplasms, spindle-cell carcinomas, and melanomas.

[FIGURES 1-2 OMITTED]

KS in HIV-infected patients can be treated with highly active antiretroviral therapy, salivary gland chemotherapy, and radiation and/or complete surgical excision.

Suggested reading

Castle JT, Thompson LDR. Kaposi sarcoma of major salivary gland origin. A clinicopathologic series of six cases. Cancer 2000;88:15-23.

Pauk J, Huang ML, Brodie SJ, et al. Mucosal shedding of human herpesvirus 8 in men. N Engl J Med 2000;343:1369-77.

>From the Department of Pathology, Beth Israel Deaconess Medical Center, Boston.