The application of the metalophil method for the demonstration of histiocytes.

The metalophil method has been performed on 250 sections of a wide variety of inflammatory and neoplastic lesions in which different types of histiocytes might be encountered. In lymph nodes, dendritic histiocytes related to the B-lymphocyte system were consistently metalophil. They appeared as small cells with slender extensions in lymph nodes with follicular hyperplasia and/or sinus histiocytosis and in some cases of Hodgkin's lymphomas or as larger pleomorphic cells in primary or secondary malignancies of lymph nodes. Small, rounded cells were seen in some cases of marked paracortical reaction, in dermatopathic lymphadenitis and in some cases of mycosis fungoides. These cells most probably represented Langerhans cells and interdigitating reticulum cells, which are related to the T-lymphocyte system. Interdigitating cells become metalophil when they are activated or proliferating. Epithelioid cells in different benign and malignant lesions were metalophil like the sinus histiocytes of the lymph nodes, the Kupffer cells of the liver and the alveolar histiocytes in the lung. Foreign-body giant cells in lymph nodes after lymphography were also metalophil. The sinus lining cells lymph nodes were also well-delineated. Histiocytes of malignant histiocytic proliferations were sometimes metalophil as were the so-called histiocytes in malignant fibrous histiocytomas. Epithelial cells, particularly the basal cells of squamous epithelium often take up the silver. Carcinoma cells were sometimes metalophil and the method appeared not to be of value in the differentiation between metastatic carcinomas and lymphomas. The most promising application seems to be the study of the distribution of dendritic histiocytes in malignant proliferations of B-lymphocytes.