Immunohistochemistry of GCDFP-24 and zinc alpha2 glycoprotein in benign sweat gland tumors

The immunohistochemical localization of two other proteins that are present in breast gross cystic disease fluid, GCDFP-24 and zinc alpha 2 glycoprotein (Zn2GP), were studied in normal skin and in 41 benign sweat gland tumors. GCDFP-24 was localized to apocrine glands. There was no staining of eccrine glands or ducts. There was positive staining in the following sweat gland tumors: apocrine hidrocystoma (four of five), hidradenoma papilliferum (two of four), syringocystadenoma papilliferum (six of seven), mixed tumor (one of one), and glandular elements of cylindroma (one of four). No staining for GCDFP-24 occurred among the following SGT: eccrine hidrocystoma (two cases), eccrine poroma (three cases), syringoma (eight cases), eccrine spiradenoma (two cases), or clear cell hidradenoma (five cases). Zn2GP was localized to both apocrine glands and eccrine glands. Positive staining was seen in the following SGT: apocrine hidrocystoma (five of five), hidradenoma papilliferum (two of four), syringocystadenoma papilliferum (four of seven), mixed tumor (one of one), cylindroma (one of four), eccrine spiradenoma (two of two), and clear cell hidradenoma (one of five). No staining for Zn2GP was seen in the following SGT: eccrine hidrocystoma (two cases), eccrine poroma (three cases), or syringoma (eight cases). GCDFP-24 appears to be a discriminant of apocrine differentiation and function. Zn2GP was expressed predominantly in tumors of apocrine differentiation. However, it was also expressed in some tumors of eccrine differentiation.