Immunohistochemical study of congenital gingival granular cell tumor (congenital epulis).

The congenital gingival granular cell tumor (CGGT) or congenital epulis is a rare lesion of unknown origin found only in newborn infants. The tumor consists mainly of large eosinophilic granular cells arranged in solid nests that are separated by thin fibrovascular areas. In addition, there are some spindle-shaped cells and medium-sized polygonal cells (so-called interstitial cells) among the neoplastic granular cells. Three CGGTs were investigated with a panel of poly- and monoclonal antibodies, using immunoperoxidase methods on formalin fixed paraffin embedded sections. Neoplastic granular cells of these three cases show cytoplasmic staining for neuron-specific enolase (NSE) and vimentin. However, all other reactions were negative. Our results suggest that the lesion may be derived from uncommitted nerve-related mesenchymal cells. On the other hand, interstitial cells show strong S-100 protein-, cytokeratin-, vimentin-, and NSE-immunostainings, and these cells are consistent with neuroendocrine nature. The presence of a biphasic cell population with granular cells and interstitial cells must be considered the main immunohistochemical feature.