Monocyte/Macrophage‐directed antibodies Ki‐M3 and Ki‐M7 detect renal‐cell carcinomas

Monoclonal antibodies (MAbs) Ki-M3 and Ki-M7, which detect cells of the human monocyte/macrophage lineages, were tested using immunohistochemistry on a series of benign and malignant human tumors (n = 43). Positive staining was detected in all renal-cell carcinomas (n = 19 positive for both Ki-M3 and Ki-M7), a few cases of breast carcinoma (n = 6 for Ki-M3; n = 2 for Ki-M7), in 1 case each of prostatic carcinoma (Ki-M3) and prostatic adenoma (Ki-M3), and in 1 case of endometriosis (Ki-M3). In normal human kidney Ki-M3 and Ki-M7 reacted with proximal tubules and parts of the distal tubules and with the loop of Henle. The Ki-M3 and Ki-M7 MAbs proved useful in detecting renal-cell carcinomas and in distinguishing these tumors and their metastases from morphologically similar neoplasms: in addition, our study further hints that renal cell carcinomas are derived from tubular epithelial cells.