Undifferentiated Tumors: An Immunohistochemical Analysis on Biopsies

Immunohistochemical staining was performed on 145 biopsies with a diagnosis of undifferentiated or poorly differentiated tumor in order to classify them into lymphoid, epithelial, or mesenchymal in origin. It was possible to arrive at a histogenetic diagnosis on immunostaining in 85.5% of cases. Immunostaining confirmed the diagnosis in 32.4% and contributed to diagnosis in 53.1%. Malignant lymphoma was the most common diagnosis (35.9%), followed by carcinoma (23.4%). A panel of antibodies consisting of anti‐common leucocyte antigen (LCA), anti‐epithelial membrane antigen (EMA), anti‐cytokeratin (CK), anti‐low to intermediate molecular weight cytokeratin (CAM 5.2), anti‐S‐100 protein (S‐100), and anti‐vimentin (VM) may resolve, to a large extent, some of the common diagnostic problems. © 1994 Wiley‐Liss, Inc.