Medullary and mixed medullary-papillary carcinoma of the thyroid gland.

Concurrent medullary and papillary carcinomas of the thyroid gland are rare and occurrence of the medullary and medullary-papillary carcinoma, as far as we know, has not been previously described. The medullary carcinoma was found in the upper part of the right lobe and the mixed medullary-papillary carcinoma in the left lobe of thyroid gland. Immunohistochemistry revealed calcitonin positivity in the medullary parts of the carcinoma and thyroglobulin positivity in papillary structures. Both light microscopy and immunohistochemistry observation distinguished these two cell lineages. The patient was treated with radiotherapy but died 18 months after first symptoms. Metastases were identified in the liver, mediastinal lymph nodes and soft tissues and micro-metastases in the lungs. The authors discuss histogenesis of mixed thyroid carcinomas.