Follicular lymphoid hyperplasia of the oral cavity representing progressive transformation of germinal center.

Follicular lymphoid hyperplasia (FLH) of the oral cavity is a rare and poorly understood lymphoproliferative disorder. We present a case of FLH of the oral cavity presenting with progressive transformation of germinal center (PTGC). The patient was a 49-year-old Japanese woman presenting with a hard mass in the right cheek. The resected specimen contained numerous lymphoid follicles with active germinal centers and a portion of the lymphoid follicles exhibited PTGC. The PTGCs contained a few large lymphoid cells resembling lymphocytic and histiocytic Reed-Sternberg cells of nodular lymphocyte-predominant Hodgkin lymphoma. The PTGC was surrounded by groups of epithelioid cells. In situ hybridization studies demonstrated strong expression of Epstein-Barr virus (EBV)-encoded small RNA in scattered large lymphoid cells in the PTGC. Although the etiology of FLH of the oral cavity remains unclear, the present case suggests that a subset of FLH of the oral cavity appears to be an EBV-associated lymphoproliferative disorder.