Metastatic mesothelioma to the thyroid

Our plain-English summary of Metastatic mesothelioma to the thyroid, by S.N. Rao, A. Swami, A. Khan, et al (CytoJournal, 2014).

The study

• Authors: S.N. Rao, A. Swami, A. Khan, M. Toke, G. Whalen, A. Fischer, M.S. Torres
• Journal: CytoJournal
• Published: 2014;11:11
• Type of article: Case report
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A 69 year-old male patient with a history of malignant mesothelioma treated with chemotherapy and surgical resection with removal of the right lung and right pleural pneumonectomy was clinically in remission for 1 ½ years. A positron emission tomography (PET) scan revealed limited uptake in the right pleural space, thought to represent post-surgical changes, and uptake in the left thyroid lobe. Thyroid ultrasound revealed a solid left lobe nodule with peripheral vascularity and absent microcalcifications. Fine needle aspiration cytology showed a microfollicular arrangement of cytologically bland cells with variable Hürthle cell changes initially interpreted as suspicious for Hürthle cell neoplasm. Review at multidisciplinary conference raised the possibility of metastatic mesothelioma, supported by immunohistochemical studies in the cell block. The patient opted for left hemithyroidectomy with isthmusectomy which confirmed malignant mesothelioma. Repeat PET scan 6 months later revealed no further uptake in the thyroid bed, with limited uptake in the right pleural space. Metastatic tumors to the thyroid are uncommon with only one previous description of metastasis to the thyroid by mesothelioma. Metastasis of cytologically low grade tumors such as mesothelioma present problems for cytology due to the potential for overlap with the variable appearances of thyroid neoplasms. The value (if any) of ancillary tests, including mutation testing, expression profiling and immunohistochemistry is discussed.

In plain English

This case report described one patient, a 69-year-old Caucasian man with a 40 pack-year smoking history. His malignant mesothelioma of epitheloid type was confirmed on pleural biopsy. The article does not mention asbestos exposure. He received four cycles of chemotherapy with carboplatin and pemetrexed, then surgery (thoracotomy with pleural pneumonectomy). The 13 hilar and 41 mediastinal lymph nodes removed were all negative. A PET scan one and a half years later showed an active nodule in the left thyroid lobe. A needle sample of the nodule was first diagnosed as suspicious for Hürthle cell neoplasm, a thyroid tumor. On review at a multidisciplinary conference, a second cell population was found that stained positive for CK 5/6 and calretinin. Removal of the left thyroid lobe confirmed multiple microscopic foci of metastatic mesothelioma. A follow-up PET scan showed no further uptake in the thyroid bed and limited uptake in the right pleural space. The authors concluded that metastases should always be considered in patients with a previous history of cancer, and that immunohistochemistry may be required to tell metastases from primary tumors.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (single patient)
• Who was studied: One 69-year-old Caucasian man, treated at the University of Massachusetts, Worcester, MA, USA. He had malignant mesothelioma of epitheloid type confirmed on pleural biopsy.
• Exposure: Not reported. The article does not mention asbestos or any occupational exposure. It records a 40 pack year smoking history.
• Main results:
  • At surgery, 13 hilar and 41 mediastinal lymph nodes were removed from the patient, and all were negative on pathology.
  • A follow-up PET scan one and a half years after treatment showed a fluorodeoxyglucose-avid nodule in the patient's left thyroid lobe (SUV 6). On ultrasound the nodule was a 2.9 cm × 1.55 cm × 1.98 cm solid, isoechoic nodule.
  • The needle aspiration (FNA) of the thyroid nodule was initially diagnosed as suspicious for Hürthle cell neoplasm.
  • In the cell block, staining for CK 5/6 and calretinin was positive in the potential mesothelial cell population and negative in the Hürthle cell population. The reverse was found for TTF-1 and thyroglobulin.
  • Left hemithyroidectomy with isthmusectomy confirmed multiple microscopic foci of metastatic mesothelioma, again positive for CK 5/6 and calretinin and negative for TTF-1 and thyroglobulin.
  • The post-operative PET scan showed no further uptake in the thyroid bed and limited uptake in the right pleural space.
  • The authors stated that, to the best of their knowledge, this was the second reported case in which metastatic mesothelioma to the thyroid was diagnosed before death.
• The authors' conclusion: The authors concluded that metastatic tumors to the thyroid are rare and may closely mimic primary thyroid neoplasms. They stated that metastases should always be considered in patients with a previous history of cancer, and that immunohistochemistry may be required to distinguish metastases from primary tumors.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Chemotherapy, Surgical Resection, Pneumonectomy, Ultrasound, Cytology, Neoplasm, Cell Block.

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