Tumors Metastatic to Thyroid Neoplasms : A Case Report and Review of the Literature

Abstract EN

Metastasis into a thyroid neoplasm—tumor-to-tumor metastasis—is exceedingly rare.

We describe the 28th documented case of a tumor metastatic to a thyroid neoplasm and review the literature on tumor-to-tumor metastasis involving a thyroid neoplasm as recipient.

All cases showed a recipient thyroid neoplasm with an abrupt transition to a morphologically distinct neoplasm.

Metastasis into primary thyroid neoplasm was synchronous in 33% of cases and metachronous in 67%.

Follicular adenoma was the most common recipient thyroid neoplasm overall (16/28), and papillary thyroid carcinoma was the most common malignant recipient neoplasm (9/28).

Of the 9 recipient papillary carcinomas, 6 were follicular variants.

Renal cell carcinoma was the most common neoplasm to metastasize to a primary thyroid neoplasm (9/28), followed by lung (6/28), breast (5/28), and colon (3/28) carcinoma.

Tumor-to-tumor metastasis should be considered whenever a dimorphic pattern is encountered in a thyroid tumor.