Clinico-pathologic study of pulmonary metastasis of differentiated thyroid carcinoma: age-, sex-, and histology-matched case-control study.

From 1952 to 1984, 70 primary cases of differentiated thyroid carcinoma with pulmonary metastasis were treated. Of these, histopathological sections were reviewed in 59 cases (metastasis group). Fifty-nine age-, sex- and histology-matched cases without pulmonary metastasis were chosen as controls (control group). Poorly differentiated features of tumor cells were observed in 57.6% of the cases in the metastasis group but in only 27.1% of the control group (P < 0.001). In contrast, solid and/or trabecular growth patterns were noted in 45.8% of the cases in the metastasis group and 52.5% of the control group (P > 0.30). No difference in the incidence of vascular or capsular invasion was seen between the two groups. These findings suggest that the poorly differentiated features of tumor cells rather than the solid and/or trabecular growth pattern or vascular invasion of the tumor are more important as histopathologic characteristics of differentiated thyroid carcinoma with pulmonary metastasis.