PMC6556265_01
Enhanced CT and PET-CT before surgery. CT demonstrates spread of the mass to the tracheoesophageal groove, suggesting invasion of the left recurrent laryngeal nerve (a). PET-CT shows focal uptake in the left thyroid lobe, with no evidence of distant metastasis (b). The mass is indicated by arrows. CT, computed tomography; PET, positron emission tomography.
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Figure 1(a)). Fine-needle aspiration cytology of the thyroid tumor showed a few clusters of elongated tumor cells with hyperchromatic dark nuclei on a background of benign hepatocytes, and the mass was reported as metastatic adenocarcinoma. Positron emission tomography-CT showed focal uptake in the left thyroid lobe with no evidence of distant metastasis (Figure 1(b)).
The operative field after left hemithyroidectomy with resection of the left RLN. The left RLN was cut around its entry to the larynx. We then performed an ansa cervicalis-to-RLN anastomosis to reinnervate the left vocal fold. The arrows indicate the anastomosis. The asterisk indicates the trachea. The double asterisk indicates the cricothyroid muscle. RLN, recurrent laryngeal nerve.
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We then performed a hemithyroidectomy with resection of the left RLN and immediate reconstruction using the ansa cervicalis nerve (Figure 2).
Pathologic examination of the excised mass. Hematoxylin and eosin staining of excised mass showed a normal thyroid goiters and adenocarcinoma (a) similar to that in the sigmoid cancer specimen (b). Immunohistochemistry of CDX2 for excised mass was positive for adenocarcinoma and negative for thyroid goiters (c), while immunohistochemistry of both thyroglobulin (d) and TTF-1 (e) was negative for adenocarcinoma and positive for thyroid goiters.
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Hematoxylin and eosin staining of the tumor showed a normal thyroid goiter and adenocarcinoma similar to that in the sigmoid cancer specimen (Figures 3(a) and 3(b)). TTF-1 (thyroid transcription factor 1) (Figures 3(c)-3(e)), which confirmed a colorectal origin. The diagnosis was solitary metastasis of sigmoid cancer to the thyroid gland.