PARAFFIN SECTION DETECTION OF THE C-KIT GENE-PRODUCT (CD117) IN HUMANTISSUES - VALUE IN THE DIAGNOSIS OF MAST-CELL DISORDERS

The c-hit gene product (CD117) is known to be expressed by a variety o f normal human tissue cell types, including breast epithelium, germ ce lls, melanocytes, immature myeloid cells, and mast cells. To further c haracterize the expression of this antigen, 117 normal human tissues a nd 576 human tumors were studied by paraffin section immunohistochemis try. Varying degrees of CD117 expression were identified in various no rmal cells and in 53% of all tumors studied. In most cases (42% of tot al), CD117 expression was weak. Expression was most common in mast cel l disease (100%), testicular germ cell tumors (100%), endometrial carc inomas (100%), papillary and follicular thyroid carcinomas (100%), sma ll cell carcinomas (91%), malignant melanomas (90%), and ovarian epith elial carcinomas (87%). Strong immunoreactivity was only identified in cases of mast cell disease (11 of 11 cases), serous ovarian carcinoma (3 of 16), malignant melanoma (2 of 40), small cell lung carcinoma (o ne of seven), and adenoid cystic carcinoma (one of one). Although the pattern of reactivity was primarily cytoplasmic, a membrane staining p attern was seen in a subset of cases, and strong membrane staining was identified in normal mast cells and all cases of mast cell disease. T he lack of tumor specificity of weak expression of this antigen limits its diagnostic utility in most cases. However, the strong membrane re activity for CD117 identified in mast cells may be useful in the diagn osis of mast cell disorders. Copyright (C) 1998 by W.B. Saunders Compa ny.