Ultrastructural localization of carcinoembryonic antigen (CEA) glycoproteins and epithelial membrane antigen (EMA) in normal and neoplastic sweat glands.

Glycoproteins of the carcinoembryonic antigen family (CEA) and epithelial membrane antigen (EMA) are established markers for glandular and mucosal tissues. However, their precise ultrastructural distribution in sweat glands has not been determined as yet. Therefore, normal human skin, 19 cases of various sweat gland neoplasms, Paget's disease, and cutaneous metastases of visceral carcinomas were stained with well-defined antibodies using a postembedding immunogold technique. In some cases, a new method of re-embedding paraffin material for immunoelectron microscopy was applied. In normal sweat glands, immunoreactivity of the endoplasmic reticulum and vesicles indicated biosynthesis and processing of CEA and EMA. Along the luminal surfaces both CEA and EMA represented an integral part of microvilli. However, a differential expression of CEA and EMA was demonstrated in apocrine epithelia, mucous cells of eccrine glands, and sweat ducts. In fetal glands, CEA was associated with formation of secretory and ductal lumina. The overall cellular distribution of CEA and EMA was highly preserved in benign sweat gland neoplasms whereas malignant neoplasms were characterized by loss of protein targeting and cellular polarity. In conclusion, these immunoelectron microscopical findings suggest a role of CEA and EMA for cell differentiation and secretory mechanisms of sweat gland epithelia.