Abstract: It is disclosed herein that antibodies specific for preproproteins or preproteins, which are synthesized by certain types of cells or tissues, can be used in immunohistochemistry assays to discriminate between the intracellular component of the protein (including the preproprotein, preprotein and/or proprotein forms of the protein) from the secreted component of the same protein. Accordingly, provided herein is an immunohistochemical method for specific detection of the intracellular form of a protein in a biological sample using an antibody specific for the preproprotein or preprotein form of the protein. In particular examples, the protein is albumin or an immunoglobulin light chain. Also disclosed herein are preproprotein-specific ore preprotein-specific antibodies that can be used to detect specific cell types, tissue lesions or other pathological foci and metastases by IHC. In particular, antibodies that specifically bind human preproalbumin, but do not bind the secreted form of albumin are disclosed.