An immunohistochemical study of lysozyme, CD-15 (Leu M1), and gross cystic disease fluid protein-15 in various skin tumors. Assessment of the specificity and sensitivity of markers of apocrine differentiation.

We investigated immunohistochemically the localization of lysozyme and Leu M1 in normal skin, 76 cases of benign sweat gland tumors, 28 cases of malignant sweat gland tumors, 23 cases of extramammary Paget's disease, 7 cases of sebaceous carcinoma, 6 cases of malignant trichilemmoma, 10 cases of squamous cell carcinoma, and 10 cases of basal cell carcinoma and compared the results with those for gross cystic disease fluid protein (GCDFP)-15 to assess the sensitivity and specificity of our assay conditions for apocrine differentiation. Normal apocrine glands were stained with all three antibodies, while eccrine glands were positive only for GCDFP-15, and other portions of normal skin were not stained with any of the antibodies used. In neoplastic tissue thought to be from apocrine tumors, antibodies raised against lysozyme and GCDFP-15 had a greater specificity (100%) for apocrine differentiation, while Leu M1 had a greater sensitivity (88%). Tissues that were stained with two or three of these antibodies appeared to exhibit apocrine differentiation. In the tumors examined, the specificity for apocrine differentiation was 100% and the sensitivity for such differentiation was 92% by these criteria. According to these criteria, some cases of syringocystadenoma papilliferum, primary mucinous carcinoma of the skin, and extramammary Paget's disease with underlying adenocarcinoma showed apocrine differentiation.