CONGENITAL EPULIS AND GRANULAR-CELL TUMOR - A HISTOLOGIC AND IMMUNOHISTOCHEMICAL STUDY

Objectives. Although it is now reasonably certain that granular cell t umors derive from Schwann cells, the histogenesis of congenital epulis , which is largely isomorphic with granular cell tumor, remains unclea r. A study was undertaken to compare the immunophenotype of these tumo rs with particular emphasis on the expression of matrix proteins and m acrophage markers because such information is not available in the lit erature. Study design. Four granular cell tumors and two congenital ep ulis were immunostained with a panel of 29 antibodies. Two congenital epulis and one granular cell tumor were investigated by electron micro scopy, the latter also by immunoelectron microscopy. Results. Many sim ilarities in immunostaining were found, for example, both tumor types were CD68+, Ki-M1P+, lysozyme-, vimentin+, fibronectin+, laminin+, lec tin PHAE+, and lectin WGA+. However, differences were also noted, for example, granular cell tumor was always S100 protein+, but only one co ngenital epulis case was reactive (weak reactivity after microwave tre atment), and staining with the proliferation markers anti-proliferatin g cell nuclear antigen and MIB 1 was found only in congenital epulis. Both tumor types exhibited pericellular and diffuse cytoplasmic staini ng For fibronectin and laminin. Conclusions. The hypothesis that conge nital epulis and granular cell tumor would exhibit similar reactivity for macrophage markers was confirmed: both were reactive with anti-CDb 8 and Ki-M1P and nonreactive with MAC387, anti-lysozyme, and 3A5. Intr acytoplasmic staining for fibronectin and laminin, which has not been described previously in these tumors, appears to be a characteristic f eature common to both tumors. This finding suggests that there could b e a disturbance of synthesis and secretion of extracellular matrix pro teins or a derangement of their receptor systems. This theory could be supported by the finding of intracytoplasmic CD49e-positive material in two cases.