Congenital leiomyomatous epulis: A case report with immunohistochemical study

The histologic and immunohistochemical findings of an extremely rare case o f congenital soft tissue mass on the alveolar ridge in an infant are report ed. The lesion clinically mimicked an ordinary congenital epulis (congenita l granular cell epulis, granular cell tumor of the newborn); however, histo logically it consisted of a conglomerate of spindle-shaped cells, akin to s mooth muscle cells, which formed interlacing and whorled fasciculi. Nerve f ibers with myxoid degeneration, capillaries and muscle walled small vessels intermingled with fasciculi of spindle-shaped cells. The border between th e conglomerate of spindle-shaped cells and the surrounding connective tissu e was not evident. Immunohistochemically, most of the spindle-shaped cells were intensely positive for antibodies to alpha-smooth muscle actin, HHF-35 and desmin. These findings suggest that the lesion was composed of mature smooth muscle cells that were of hamartomatous or choristomatous nature. Th e term 'congenital leiomyomatous epulis' is proposed.