Nucleolar organizer regions in paragangliomas of the head and neck.

The clinical behavior of head-and-neck paragangliomas cannot be accurately predicted using standard histologic criteria. Immunohistochemical profiles have proved to be prognostically helpful; however, other independent indicators of prognosis are needed. Tissue markers of proliferative activity include argyrophilic nucleolar organizer regions (AgNOR), which are proteins specifically associated with loops of transcriptionally active ribosomal DNA. Fifteen paragangliomas of the head and neck were divided into solitary nonrecurrent (n = 8), recurrent or locally invasive (n = 4), and multiple (n = 1), or malignant (n = 2) groups. The mean AgNOR count per cell was statistically different between the solitary nonrecurrent and the combined other poorer prognosis groups, suggesting that it may be useful as an independent indicator of biologic behavior. The wide variation in AgNOR counts within groups and the overlap of counts between groups limit, however, the predictive value of this technique for individual tumors.