Thyroid metastasis from cervical carcinoma

There have been very few reports of thyroid metastasis from cervical carcinoma. This article reports a case of metastasis from cervical carcinoma. A 69-year-old woman with a history of cervical cancer presented to our department with right cervical swelling. She had suffered from paralysis of the left recurrent laryngeal nerve after undergoing left hemithyroidectomy 16 years ago. Computed Tomography (CT) and magnetic resonance imaging scans revealed a right thyroid tumor with bilateral enlargement of the cervical lymph nodes. Fluorodeoxyglucose positron emission tomography/CT imaging revealed high uptake in the right thyroid tumor, cervical lymph nodes, and right iliac bone. Fine-needle aspiration cytology revealed atypical epithelial cells with a high nuclear/cell ratio and hyperchromatic nuclei, which resembled cervical cancer cells. Given the risk of airway obstruction and dysphagia, the patient underwent tracheostomy, right hemithyroidectomy, and neck dissection for preserving the quality of life. Pathological examination revealed normal thyroid tissue with p16-positive atypical epithelial cells, which suggested thyroid metastasis from the cervical cancer. The patient has remained alive without any symptoms for 5 postoperative months.


Case presentation
A 69-year-old woman presented to our department with a 2-month history of progressive swelling in the right anterior neck. Sixteen years ago, the patient had undergone a left hemithyroidectomy for a benign thyroid tumor at another hospital, which resulted in persistent paralysis of the left recurrent laryngeal nerve. Further, she had undergone hysterectomy followed by chemoradiotherapy for cervical squamous cell carcinoma 5 years before admission.
The patient refused further examination and treatment for the cervical cancer.
Physical examination revealed a hard nodule with a diameter of 5 cm in the right anterior cervical lesion. A laryngeal fiberscope revealed paralysis of the left, but not right larynx. Contrast-enhanced Computed Tomography (CT) revealed an irregular calcified tumor in the right thyroid gland and swollen lymph nodes in the bilateral neck ( Fig. 1 A---C). Magnetic resonance imaging revealed a right thyroid tumor with low signal intensity on T1-weighted images and iso-signal intensity on T2-weighted images; moreover, the tumor showed heterogeneous staining with gadolinium ( Fig. 1 D---F). Fluorodeoxyglucose Positron Emission Tomography/CT (FDG-PET/CT) showed abnormal FDG accumulation in the right thyroid gland, bilateral neck lymph nodes, and right iliac bone ( Fig. 1 G---H). Fine Needle Aspiration Cytology (FNAC) of the thyroid revealed atypical epithelial cells with a high nuclear/cell ratio and hyperchromatic nuclei, which resembled cervical cancer cells.
Given the risk of airway obstruction and dysphagia, the patient underwent tracheostomy and right hemithyroidectomy. A right neck dissection was simultaneously performed due to adherence of the thyroid tumor to the cervical lymph nodes. Under general anesthesia, a J-shaped skin incision was made from the right mastoid process to the anterior neck. The sternocleidomastoid muscle and internal jugular veins were resected due to tumor invasion. The thyroid tumor invaded the trachea and esophagus, which were both preserved following their surface resection. Pathological examination revealed normal thyroid tissue with squamous cell carcinoma (Fig. 2 A---B). Since the atypical epithelial cells were positive for p16, which is a surrogate marker of Human Papillomavirus (HPV), the patient was diagnosed with thyroid metastasis from cervical cancer (Fig. 2C). The patient has remained alive without any symptom for 5 postoperative months.

Discussion
Cervical cancer is related to HPV and expresses p16 as a surrogate marker for HPV infection. Our patient had a history of cervical cancer and did not present with other HPV-related cancers, including oropharyngeal cancer. Since histological  examination revealed squamous cell carcinoma with p16 staining, the patient was diagnosed with thyroid metastasis from cervical cancer.
Metastasis of cervical cancer to the thyroid gland is rare, with only 14 cases having been reported, including our case (Table 1) 3---14 . The mean age of the reported patients was 55 years (range: 36---72 years; n = 14). The histology of cervical cancer was squamous cell carcinoma in nine cases, adenocarcinoma in two cases, neuroendocrine carcinoma in two cases, and poorly differentiated carcinoma in one case. Moreover, the laterality of the thyroid tumor was bilateral, right, and left in one, six, and four patients, respectively. The median latency between the initial diagnosis of cervical cancer and its metastases to the thyroid gland was 15 months (range: 5---12 years; n = 12). FNAC was performed in nine cases; among them, seven cases were considered positive for malignant cells. Thyroidectomy was performed in seven patients to preserve their quality of life. Distant metasta-sis other than thyroid tumors occurred in 10 out of the 14 patients (71%); among them, eight patients died within a year due to multiorgan metastasis. Since thyroid tumors can obstruct the airway and digestive tract, it is important to carefully treat metastasis to the head and neck region. Since there are no international guidelines for the management of thyroid metastases from cervical cancer, individualized treatment interventions including tracheostomy and surgical resection should be considered to relieve symptoms and improve quality of life. Since our patient had left recurrent laryngeal nerve paralysis and thyroid tumor invasion near the right recurrent laryngeal nerve, a tracheostomy was performed to secure the airway. Additionally, thyroidectomy and neck dissection were performed to preserve swallowing function by releasing the esophagus from the adhered tumor. Although these surgeries are not curative treatments for cervical cancer with multiple metastases, palliative tumor reduction could improve the quality of life.

Conclusion
This article reports a rare case of thyroid metastasis from cervical carcinoma. Although the prognosis of cervical cancer with metastasis is generally poor, surgical resection may be useful for securing the airway and digestive tract in order to temporarily improve the quality of life of patients with metastatic thyroid cancer.

Funding
The authors received no financial support for the publication of this article.