[Secondary neoplasms of the thyroid gland].

SECONDARY neoplasm of the thyroid gland is uncommon, but perusal of the literature reveals a higher incidence than might be generally assumed. Muller (i892) reported the incidence of macroscopic metastatic carcinoma of the thyroid as 1.5%11 in all cases of carcinoma, regardless of primary site. The incidence in cases of sarcoma was 3.i%. Kitain (I922) recorded the incidence in regard to carcinoma to be 3 I% and Willis (I93I) as 5.2%. The latter author, however, stated that these figures were based on routine sectioning of the thyroid gland. Mortensen, Woolner and Bennett (1956) from the Mayo Clinic examined 467 thyroid glands both macroscopically and microscopically but found only i8 cases of secondary carcinoma, an incidence of 3.9%. McGavack (I95I) found 125 cases of secondary carcinoma of the thyroid but made no mention of its incidence. Naylor (I959) examined 300 cases of generalized lymphoblastoma and found the thyroid to be involved in 17.7%Of primary tumours resulting in metastasis within the thyroid gland McGavack found the commonest to be hypernephroma, gonadal tumours and cancer of the large bowel. Mortensen, Woolner and Bennett, in their series of i8 cases, however, found the commonest to be tumours of the lymphatic system, the breast, lung and rectum; the only other neoplasms to metastasize to the thyroid were ovary, kidney, colon and larynx. In all these I8 cases metastasis had occurred in other organs as well. Bruce and Michie reviewed I,6oo patients who had undergone thyroidectomy and found four cases of secondary carcinoma: two arose from hypernephroma, one from cancer of the colon and one from cancer of the rectum. These authors also collected 22 cases from the literature of secondary hypernephroma of the thyroid: IS of these patients had post-mortem examinations and in 14 metastasis had taken place in other organs as well. The only case of solitary metastasis within the thyroid was in a patient who died immediately after thyroidectomy (see also Mortensen, Woolner and Bennett).