[Distant metastases of malignant thyroid cancer. A retrospective study of 892 cases]

In 892 patients with thyroid carcinoma, distant metastases developed in 151 cases, and these were classified according to conventional pathohistological types and--in particular--to the incidence of surgically treatable solitary sites. The aim of the present study was also to investigate whether the histological diagnosis is of value in predicting the pattern of metastatic spread. Distant metastases of anaplastic carcinoma and sarcoma were found most frequently in the lungs (70 out of 81 patients, this is 86%), with 4 cases being solitary tumors. Metastatic spread into the skeleton, however, occurred rarely (14 out of 81 patients, 17.3%), when compared with differentiated carcinoma (64.8%). Moreover, with the exception of 1 case, metastatic growth was not solitary but involved more areas in bone. On the other hand, the well differentiated carcinoma displayed a greater predilection for the metastatic spread to the skeleton: 35 cases of bone involvement were identified in 54 patients with distant metastases (64.8%), and out of these cases, 10 metastases were solitary. Metastatic spread into the lungs occurred less often (30 of the 54 patients, 55.5%) and always displayed a diffuse pattern or involved multiple sites. In some cases, solitary metastases of different histological types were also identified in other organs. Our findings suggest that the pathohistological classification appears to be of use in guiding the clinical approach to a curative extirpation of distant solitary metastases in selected patients.