Paragangliomas of the craniocervical region. An immunohistochemical study on tyrosine hydroxylase.

An immunohistochemical study on tyrosine hydroxylase (TH), a rate-limiting enzyme in the catecholamine synthesizing pathway, was made on three craniocervical region paragangliomas, two of which showed metastases to the cervical lymph nodes. In all of the original tumors, the majority of tumor cells showed positive immunostaining for TH of variable intensity in their cytoplasm regardless of their cytological features such as cellular and nuclear pleomorphism. The finding suggests that most tumor cells are capable of production of catecholamines and are derived from chief cells in the normal paraganglia. In cervical lymph nodes, however, no positive immunostaining for TH was observed in metastatic tumor cells, in contrast with the findings in the original tumors. The absence of TH immunoreactivity in metastatic tumor cells appears to be noteworthy in considering their malignant potential. Application of the TH immunohistochemistry to further cases appears important for the better understanding of this neoplasm, a catecholamine-producing tumor.