Thyroglossal duct papillary carcinoma presenting as submental neck node

INTRODUCTION

Neck swelling or neck node in sub mental area is not uncommon. It occurs mostly due to infective or malignant pathologies in oral cavity. Submental neck node mass due to thyroglossal duct cyst carcinoma is extremely rare presentation. Thyroglossal duct carcinomas (TGDC) are also rare, with less than 300 reported cases since the first report in 1915.¹ Thyroglossal duct cysts are the most common anomaly in thyroid development. They are second only to enlarged cervical lymph nodes as the cause of neck mass. Generally, duct cysts are benign, but 1% of cases may be malignant.² Thyroglossal cyst can present as a mass located: (a) between the hyoid bone and the thyroid cartilage-60%, (b) above the hyoid bone including the submental site-24%, (c) substernal region-13% and (d) intra-lingual-2%.^3,4 In a review of literature by Weiss et al, out of 115 cases of TGDC, the different types of neoplasia of thyroglossal duct described included thyroid papillary carcinoma in 81.7 per cent, mixed papillary-follicular carcinoma in 6.9 per cent, squamous cell carcinoma in 5.2 per cent, follicular and adenocarcinoma in 1.7 per cent each, and malignant struma, epidermoid carcinoma and anaplastic carcinoma in 0.9 per cent each.⁵ Our case of submental neck swelling as a sole presentation which turned out to be metastatic papillary carcinoma from thyroglossal duct is an extremely rare presentation.

CASE REPORT

A 25 year old female presented with a sub mental neck node which was noticed for 6 weeks with no history of fever or any oral lesions (Figure 1). The node was not associated with pain, variation in temperature or sudden increase in size. There was no history of dysphagia, dyspnea or hoarseness of voice. On examination, the node was 1 × 1 cm size and found to be non-tender, firm, not moving on swallowing, with no other neck swelling palpable. Ultrasound of neck showed 2 enlarged level IA lymph nodes with loss of fatty hilum within and size measuring about 14 × 8 mm and 13 × 9 mm. Also tiny hypoechoic nodules less than 3 mm were noted in both lobes of thyroid, size of both lobes of thyroid and isthmus measuring normal. Fine needle aspiration cytology (FNAC) of the sub mental neck swelling showed features suggestive of papillary carcinoma (Figure 2). The patient underwent Tc 99 Pertechnate scan in order to find the primary site and to find out the possibilities of metastases in other neck nodes. There was heterogeneous tracer uptake in the sub-mental region and normal uptake in thyroid gland, but no uptake in thyroglossal duct region (Figure 3). Patient’s thyroid profile was normal. We performed total thyroidectomy with Sistrunk’s operation with clearance of central compartment and level I. Intraoperative and post-operative period was uneventful. Histopathology report showed papillary carcinoma of thyroglossal duct region with metastatic carcinoma in level IA node and thyroid gland showing features of nodular goiter with autoimmune thyroiditis (Figure 4). The patient is under follow up for radioactive iodine treatment as the tumor was extending close to margins. We intend to publish this case report as it is a rare case.

DISCUSSION

According to a study done by Ural et al, different pathologies of a mass occurring in submental area are reactive lymphoid hyperplasia, non-Hodgkin lymphoma, dermoid cyst, abscess, sarcoidosis, hemangioma, and lipoma.⁵ Neck mass in submental area occurring due to metastases from TGDC without the swelling in primary is an extremely rare presentation. The thyroid gland descends from the foramen caecum to its location at the point below the thyroid cartilage. It leaves behind an epithelial tract known as the thyroglossal tract; this tract usually disappears during the 8–10th gestational weeks. Incomplete atrophy of the thyroglossal tract or retained epithelial cysts, create the basis for the origin of a thyroglossal duct cyst.^6,7 The histologic findings of TGDC are most commonly papillary carcinoma (75–80%), but other thyroid tumors such as follicular, Hürthle cell, and mixed papillary–follicular carcinomas have been reported.⁸ Imaging diagnostic techniques, including ultrasound, scintigraphy and CT, are usually unable to preoperatively diagnose malignant disease and fine needle aspiration yields a correct result in only 66% of the cases. Nearly 4% of TGDC were found to be locally invasive, while 11% were found to include metastasis to cervical lymph nodes. In about 20% of TGDC, carcinoma in thyroid co-existed.¹ The etiology of the papillary carcinoma arising in a thyroglossal duct is unclear. Generally, there are two theories which can explain this phenomenon, de novo origin and spread from a primary thyroid gland tumor. Most authors support the theory of primary de novo origin by the ectopic thyroid nests of the cyst wall rather than the metastatic spread from a primary thyroid gland tumor through the duct from the thyroid carcinoma, which explains our case. The other theory explains synchronous occurrence of thyroglossal duct cyst carcinoma and thyroid carcinoma, which are reported to be even rarer, as multifocal tumor.⁹ Multicentricity and multifocal growth are common in papillary thyroglossal duct carcinomas, as a second malignant lesion is present in 10% of cases with thyroid cancer.³ In case of large tumors >1 cm, or invasion through the duct cyst wall or suspect foci in the thyroid gland, or a metastases in neck node, a total thyroidectomy followed by I¹³¹ ablation and thyroid-stimulating hormone suppression is the most frequently proposed treatment.¹⁰

ACKNOWLEDGEMENTS

We acknowledge Apollo hospitals for using the medical records.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

REFERENCES

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