CLINICAL AND PATHOLOGICAL CHARACTERISTICS OF SECONDARY THYROID-CANCER

Although up to 24% of metastatic cancers have been reported to spread to the thyroid gland, metastases to the thyroid are not detected in cl inical practice in most cases. The prognosis is poor when metastatic c ancer to the thyroid occurs. The aim of this study was to examine the clinical presentation, cytopathological findings, and clinical course of secondary cancers of the thyroid. The medical records of a total of 1013 histopathologically verified thyroid cancer patients treated dur ing the period from January 1977 to December 1995 in Chang Gung Medica l Center in Linkou were analyzed retrospectively. There were 14 patien ts (1.4% of all thyroid cancers) with secondary cancers of the thyroid with a mean age of 55.3 +/- 16.7 years. All these patients underwent thyroid ultrasonography and a fine-needle aspiration cytology of the t hyroid (FNAC) before biopsy or surgical treatment. Tissue diagnosis wa s obtained by biopsy or necropsy in 12 or by thyroidectomy specimens i n 2 patients. Most of the patients died within 9 months of diagnosis e xcept for 2 patients who were lost to follow-up after transferring to another hospital and 1 patient with lymphoma. Before the surgical diag nosis, there were only 7 patients who metastatic neoplasms to the thyr oid gland were diagnosed by FNAC. Anaplastic thyroid carcinoma was dia gnosed in 5 patients. Benign nodule was diagnosed in 1 patient and lym phoma in another patient. Most of these patients had widespread metast ases to many organs, as well as the thyroid gland. As a result these p atients had very short survival times. Delayed diagnosis of the thyroi d metastasis was the main reason for the short survival period. In con clusion, most of the metastatic lesions presented as an advanced stage of primary cancers. FNAC was a useful tool in the diagnosis. Histopat hological diagnosis by surgical open biopsy is needed for the final di agnosis.