Occurrence of acid and neutral cysteine proteinase inhibitors in epidermal malignancies: immunohistochemical study.

Acid cysteine proteinase inhibitor ( ACPI ) and neutral cysteine proteinase inhibitor ( NCPI ) were localized in human epidermal malignancies by the unlabelled peroxidase-antiperoxidase complex method. Basaliomas did not contain ACPI or NCPI . In spinous, metatypic , and clear cell carcinomas of the epidermis, both inhibitors were located in the cytoplasm and sometimes on the cell membranes of the differentiated carcinoma cells. The inhibitors were not seen in the 1 or 2 most "basal" cells layers of the carcinoma islets. The locations of both inhibitors were similar, and the staining for ACPI was usually more intense than staining that NCPI .