Malignant Solitary Fibrous Tumor Metastatic to Widely Invasive Hurthle Cell Thyroid Carcinoma: A Distinct Tumor-to-Tumor Metastasis.

We illustrate a case of synchronous malignant solitary fibrous tumor of the thoracic cavity, and widely invasive thyroid Hurthle cell carcinoma. The Hurthle cell carcinoma was found to harbor distinct areas of malignant solitary fibrous tumor. This is a unique case of tumor-to-tumor metastasis that, to the best of our knowledge, has not been previously reported.