Columnar Cell Carcinoma of the Thyroid: MIB-1 Immunoreactivity as a Prognostic Factor

We report a case of columnar cell carcinoma of the thyroid. A 47-year-old Japanese man had a nonencapsulated thyroid mass that infiltrated the surrounding tissues extensively. Seventeen months after thyroidectomy he died of respiratory failure resulting from tracheal invasion. An autopsy showed distant metastases to the liver, lung, esophagus, and pancreas. Histologically, the thyroid mass consisted of tall columnar atypical cells with marked nuclear stratification, About one-fifth of tumor cells were immunopositive for M18-1. The MIB-1 -positive index of our case was extremely high, compared with that of ordinary papillary carcinoma. This case indicates that biological growth activity in columnar cell carcinoma may be similar to that of undifferentiated carcinoma of the thyroid, since the MIB-1 -positive index is close to each other.