Clinicopathologic and immunohistochemical studies of papillary thyroid microcarcinoma presenting with cervical lymphadenopathy.

Although most papillary thyroid microcarcinomas (PMCs) are of little clinical significance, patients with PMCs occasionally have an unfavorable outcome, especially when they present with bulky nodal metastasis or distant metastasis. We have attempted to identify "high-risk" PMCs by evaluating clinical, pathologic, and immunohistochemical prognostic factors. Among 190 patients with a PMC, 156 without clinically apparent nodal metastasis had a benign course. The remaining 34 patients, who presented with cervical lymphadenopathy of at least 1 cm, were studied. Three of the four patients who developed distant metastasis died of the disease, and the other died of local recurrence. All patients who developed distant metastasis or died of the disease had both nodal metastasis of at least 3 cm and a nonencapsulated type of primary lesion. All patients who developed distant metastasis showed both extracapsular extension of the metastatic lesions in lymph nodes and positive staining for transforming growth factor-beta3 (TGFbeta3) (a potent growth inhibitor) in the primary lesion. The Ki-67 (an indicator of cell proliferation) labeling indices in the primary and metastatic nodal lesions of patients who died of cancer were significantly higher than those of the others with nonfatal disease. None of the patients showed P53 (nuclear tumor-suppressor phosphoprotein) overexpression. In conclusion, patients with PMC who have both 3 cm or larger lymphadenopathy and a nonencapsulated type of primary lesion may be regarded as high-risk patients. Immunohistologic positivity for Ki-67 and TGFbeta3 in cancer cells is a potential indicator of aggressively malignant PMC.