Kaposi sarcoma following postmastectomy lymphedema.

Classical Kaposi sarcoma (KS) usually appears on lower extremities accompanied or preceded by local lymphedema. However, the development in areas of chronic lymphedema of the arms following mastectomy, mimicking a Stewart-Treves syndrome, has rarely been described. We report an 81-year-old woman who developed multiple, erythematous to purple tumors, located on areas of post mastectomy lymphedema. Histopathological examination evidenced several dermal nodules formed by spindle-shaped cells that delimitated slit-like vascular spaces with some red cell extravasation. Immunohistochemically, the human herpesvirus type 8 (HHV-8) latent nuclear antigen-1 was detected in the nuclei of most tumoral cells confirming the diagnosis of KS. Lymphedema could promote the development of certain tumors by altering immunocompetence. Although angiosarcoma (AS) is the most frequent neoplasia arising in the setting of chronic lymphedema, other tumors such as benign lymphangiomatous papules (BLAP) or KS can also develop in lymphedematous limbs. It is important to establish the difference between AS and KS because their prognosis and treatment are very different. Identification by immunohistochemistry of HHV-8 is useful for the distinction between KS and AS or BLAP.