Cellular distribution of cathepsin D in childhood tumors

Cathepsin D is an acidic endopeptidase that has been found in the cytoplasm of neurons and other cells. To test the hypothesis that the cellular content or distribution of cathepsin D may serve as a marker of neuronal differentiation in childhood neoplasia, we performed an immunocytochemical study of the cathepsin D content of tumors that occurred in 49 pediatric patients. We found diffuse, moderate to heavy staining primarily in differentiating neurogenous tumors and minimal staining in one Wilms' tumor, one Ewing's sarcoma, and one rhabdomyosarcoma. Benign reactive histiocytes stained intensely in most tumors. We concluded that although the presence of cathepsin D in malignant cells is not diagnostic of neural tumors, it may serve as a marker for cellular maturation in neuroblastomas and as a marker of macrophage infiltration in human tumors.