Secondary carcinoma of the thyroid gland.

When the cervical tumor mimics thyroid carcinoma, some cases are shown to be the primary carcinoma of other site. Four cases of secondary thyroid carcinoma, of which primary sites are adjacent organ, are studied. The characteristics of histology are squamous cell carcinoma. Squamous cell carcinoma of which primary organ seems to be thyroid often discloses metastatic neoplasm originated from the adjacent organs. Since chronically inflammatory lesion is recognized concurrently, abnormal thyroid is suggested to be congenial soil for malignant growth. Our experience indicates that the secondary carcinoma due to direct extension should be considered on diagnosing squamous cell carcinoma of the thyroid.