We report a case of a man in his 60s with metastatic lung adenocarcinoma in the thyroid and cervical lymph nodes. The lung cancer was resected 5 years prior to presentation. The metastasis mimicked primary thyroid cancer by clinical examination and CT. However, fine-needle aspiration cytology of the thyroid and the lymph node lesions favoured lung cancer metastasis rather than thyroid cancer. Left thyroid lobectomy and lymphadenectomy were performed. Pathology confirmed the presence of an adenocarcinoma in the thyroid and two lymph nodes, which was similar to the previous lung cancer. The tumour cells in the thyroid were immunohistochemically positive for TTF1 and thyroglobulin and negative for PAX8. This is the second reported case of metastatic lung cancer in the thyroid that was focally positive for thyroglobulin. This can be a pitfall in differentiating between primary thyroid tumour and metastatic lung adenocarcinoma by pathological and cytological examination.
- Head and neck surgery
- Respiratory medicine
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Contributors KY performed pathological diagnosis and had a major contribution in writing the manuscript. NH performed surgical treatment of the thyroid lesion. NT performed surgical treatment of the lung cancer. HM performed course observation and obtained written informed consent from the patient.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.