OBJECTIVETo investigate the role of clonality analysis by X-chromosome inactivation in the diagnosis of cervical lymph node metastasis from squamous carcinoma of the head and neck.

METHODSTwenty cases of clinical NOM0 squamous carcinoma of the head and neck with either pathologically confirmed or suspected occult micrometastasis in the cervical lymph node were recruited. Interested DNA samples were procured through tissue microdissection and one-step proteinase K digestion, and the clonality analysis was carried out by means of restriction enzyme digestion and amplification of human androgen receptor markers (HUMURA) to check out the status of X-chromosome inactivation. The clonal origin of the primary tumor cells and the interested cell clones in the cervical lymph node was traced by X-chromosome inactivation, and the diagnosis of cervical lymph node micrometastasis was either confirmed or ruled out.

RESULTSTumor cells from both primary and metastatic lesions were monoclonal and identical in clonal origin in 10 patients with pathologically confirmed cervical lymph node metastasis, whose metastatic tumor cells expressed EGF receptor. For 10 patients with suspected micrometastasis in the neck nodes, whose focused lesions did not expressed any EGF receptor protein by immunohistochemistry, the identical and monoclonal origin between the primary tumor and the suspected metastatic lesion in the neck node was confirmed in 6 patients, and the polyclonal origin of the neck node lesions was revealed in other 4 patients. The diagnosis of micrometastasis in the neck node was thus ascertained in 6 and ruled out in 4 suspected cases.

CONCLUSIONSExamination of X-chromosome inactivation pattern is a useful method for identification of the neck node occult micrometastasis from squamous carcinoma of the head and neck.