Classical Kaposi's sarcoma is an unusual multifocal neoplasm of vascular endothelial cell origin, and considered a less malignant, slowly-progressing tumor. Although visceral involvement is occasionally seen in HIV/AIDS patients with KS, tumor dissemination to visceral lymph nodes in classical KS is very rare. A 72-year-old woman without any other relevant past medical history presented with anorexia, weight loss, night sweats, and skin eruptions. As the rapid progression of cytopenias and lymphadenopathy were observed, bone marrow biopsy and imaging were performed. Positron emission tomography showed disseminated lymphadenopathy in the cervical, axillary, mediastinal, inguinal, and abdomino-pelvic nodal areas. Inguinal lymph node biopsy was compatible with KS, positive for CD31, CD34, and human herpesvirus-8 by immunohistochemical stain. We report a case of aggressive classical KS mimicking aggressive malignant lymphoma.