|Year : 2018 | Volume
| Issue : 2 | Page : 109-112
Primary papillary carcinoma of a thyroglossal duct cyst: A rare case
Department of Radiology, St. John's Medical College, Bengaluru, Karnataka, India
|Date of Web Publication||6-Jul-2018|
Dr. Reddy Ravikanth
St. John's Medical College, Bengaluru - 560 034, Karnataka
The incidence of papillary cell carcinoma arising in a thyroglossal duct cyst (TDC) is rare and occurs in 1% of TDCs. Due to embryological remnants of thyroid tissue located in the TDC, the same malignant tumors that develop in the thyroid tissue can also develop in the TDC. The occurrence of carcinoma of TDC, even though rare and unexpected, should always be considered an option and histologically ruled out mainly on account of the atypical localization. We report a case of papillary carcinoma arising in a TDC, presenting with an anterior neck mass in a 28-year-old woman, who underwent a Sistrunk procedure for removal of the mass with total thyroidectomy and neck dissection. Fine-needle aspiration cytology did not contribute to the diagnosis. Based on the histopathologic findings, the patient received postoperative iodine-131 ablation treatment (120 mCi). This type of carcinoma usually has a good prognosis with an overall survival rate of 95.5% at 10 years. Carcinomas of TDC demonstrate lower frequency of regional lymph node metastasis in comparison with that arising in the thyroid gland proper and can be successfully managed with surgery and careful follow-up.
Keywords: Papillary carcinoma, Sistrunk procedure, thyroglossal cyst
|How to cite this article:|
Ravikanth R. Primary papillary carcinoma of a thyroglossal duct cyst: A rare case. Sahel Med J 2018;21:109-12
| Introduction|| |
The thyroid gland in embryogenesis develops as the first pharyngeal derivative, primarily appearing as an invagination in the floor of the pharynx and then migrating caudally to the trachea. During embryogenic development, it remains attached to the tongue by the thyroglossal duct, which usually undergoes atrophy after birth. If it fails to involute, it can persist as a cyst, a duct, or ectopic tissue, which is localized in the midline between the base of the tongue and the pyramidal lobe of the thyroid gland. A remnant of a thyroglossal duct, usually a cyst thyroglossal duct cyst (TDC), is the most common congenital abnormality of thyroid gland development. The ectopic thyroid tissue in TDCs varied from 1.5% to 45% of cases. TDC is the most common congenital anomaly of the cervical midline in children and young adults. It presents from the base of the tongue to the lower part of the midline of the neck. 60% is found between the hyoid bone and the thyroid cartilage, 13% is retrosternal, 24% is above the hyoids, and 2% is submentonian. 70% is located in midline, the rest are paramedian. Half of the cases are diagnosed in adults over 20. It is claimed that ectopic thyroid tissue does not represent an increased risk of malignant transformation in comparison with the thyroid gland. The malignant neoplasm in the TDC is a very rare tumor, which encouraged us to present the case of a papillary thyroid carcinoma, arising in the ectopic thyroid tissue in the TDC, with a long follow-up period.
Papillary type thyroid carcinoma can develop in the TDC de novo with an incidence of 1% although some authors believe that the thyroglossal duct instead serves as a natural route for occult thyroid carcinoma metastases. Thyroid carcinomas originating from the TDC are mostly seen in females between the ages of 20–60 years and present as a complaint of pain at the level of the thyrohyoid membrane along the neck midline with a physical examination finding of a palpable mass without tenderness. Occasionally, the presenting sign of thyroid carcinoma is a rapidly growing mass, mimicking TDC infections. In such cases, diagnosis is usually made after histopathologic examination of a specimen from a Sistrunk resection. Ultrasound (US), computed tomography (CT), magnetic resonance imaging, and fine-needle aspiration cytology (FNAC) can be useful techniques to differentiate TDC carcinomas from simple TDC before a surgical operation 23rd January 2017.
| Case Report|| |
A 28-year-old female patient was admitted in our hospital with complaints of 6-month history of a slowly growing mass along the midline of neck. Physical examination revealed a 3 cm × 6 cm immobile mass along the neck midline over the thyrohyoid membrane. Lateral neck radiograph showed an ill-defined midline calcified lesion inferior to the level of the hyoid bone [Figure 1]. A neck US revealed a calcified heterogenic-hypoechoic solid lesion of 3 cm × 6 cm below the level of the hyoid bone, which was not related to the thyroid gland [Figure 2]a. Thyroid gland US revealed several hypoechoic nodules, the largest being 6 cm × 4 mm, with few of them containing microcalcifications in the right lobe of thyroid gland while the study identified no left lobe lesions [Figure 2]b. The US findings warranted further evaluation with Doppler and FNAC. The midline structure measured 1.6 cm3 with the absence of flow on Doppler sonography. FNAC did not contribute to the diagnosis. Contrast-enhanced CT of the neck showed a 3 cm × 6 cm midline solid-cystic mass midline infrahyoid lesion with punctate calcifications and an enhancing solid component with 1.5 cm × 1.7 cm [Figure 3].
|Figure 1: Lateral plain radiograph showing an ill-defined midline calcified lesion inferior to the level of the hyoid bone|
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|Figure 2: (a) Ultrasound image showing a calcified heterogenic-hypoechoic midline solid lesion of 3 cm × 6 cm below the level of the hyoid bone. (b) Ultrasound image showing a hypoechoic nodule in the right lobe of thyroid|
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|Figure 3: Axial plain computed tomography image showing midline solid-cystic infrahyoid lesion with punctate calcifications and bilateral cervical lymphadenopathy|
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After considering all of the clinical and radiological data, despite a histopathologic diagnosis of benign cytology for the right lobe nodule, we performed a Sistrunk procedure with total thyroidectomy and central neck exploration due to suspicion of simultaneous de novo development of papillary carcinoma in the TDC and the thyroid gland. Informed consent was obtained before the procedure. During the Sistrunk procedure, a solid mass invading the infrahyoid muscle group was encountered, and gross total resection of the tumor was performed. A total thyroidectomy operation was performed. During central neck exploration, samples of the suspected lymph nodes were sent for frozen section pathology, the results of biopsied cervical lymph nodes revealed no malignancy. After completion of the exploration, the central neck was dissected and additional specimens were sent to pathology.
Pathologic examination identified the thyroid and thyroglossal duct specimen as containing primary papillary carcinoma. Histopathology revealed the nodule which was seen on the cut section of thyroglossal cyst tissue; the tumor was located within cysts, composed of complex branching true papillae that contain fibrovascular stalk. The papillae were lined by neoplastic epithelial cells with enlarged, clear “Orphan Annie eye” nuclei and some of them had nuclear grooves. The tumor cells were positive for CK 19, Galectin-3, and HBME-1 which were compatible with papillary carcinoma. After the operation, a radioactive iodine (RAI-131) dose of 120 mCi was administered as adjuvant therapy. Postoperatively, the iodine-131 uptake scan performed 6 weeks later to look for other potential metastasis revealed none. After RAI treatment, the patient had an undetectable thyroglobulin level at the 6-month follow-up.
| Discussion|| |
TDC is the most common congenital mass along the neck midline. Papillary carcinoma is the most common malignant tumor of both the TDC and the thyroid gland. Papillary carcinoma originating from the TDC usually manifests a slowly growing mass along the neck midline with a low propensity for distant metastases and having good prognosis. Papillary carcinoma from the thyroid gland also has good prognosis. A controversial issue is whether papillary carcinoma in the TDC develops de novo or as a type of metastasis from an occult tumor nidus in the thyroid gland. A limited number of reported cases describe the presentation of a TDC papillary carcinoma accompanied by a thyroid gland papillary carcinoma. It is difficult to differentiate primary papillary carcinoma of the TDC from metastases of an occult carcinoma of the thyroid gland. This differentiation, however, can play a crucial role in the treatment strategy in terms of including thyroidectomy as part of the treatment strategy versus TDC total resection alone.
In our case, the papillary carcinoma in the TDC was classical in type with a de novo origin. However, the frequency of thyroid carcinoma in the TDC seems to be increasing; indeed, several cases, in which nodules were also found within the thyroid gland have been reported, making thyroid gland evaluation an important component of the workup. The success of a definitive surgical procedure for papillary carcinoma of the TDC is dependent on the preoperative radiologic and histopathologic evaluation as well as the intraoperative tumor evaluation. A Sistrunk procedure with clear surgical margins and adjunct treatment with RAI are the standard regimen for TDC papillary carcinoma. Total thyroidectomy and central neck dissection should be added to the treatment when a nodule is found in the thyroid gland during inspection, palpation, and intraoperative evaluation. Surgery, external radiation therapy, or RAI are the treatments of choice in patients with local relapse or metastasis.
Thyroid carcinoma presenting with cervical lymphadenopathy as a sole presentation is uncommon. Metastatic cervical lymph nodes could potentially arise from several primary sources in the head and neck region. Investigations may fail to reveal a primary carcinoma in the thyroid gland, and hence, FNAC or biopsy is of the primary importance to establish the origin of primary tumor. Once established, the management should include complete resection of the primary and metastatic carcinoma, postoperative RAI scanning and possible RAI treatment, and lifelong replacement thyroxine.
The challenge is whether to complete the procedure with thyroidectomy or not, when laboratory findings have shown details of carcinoma in the thyroglossal cyst. All patients must have follow-up with a neck scan and be reassessed every 6 months during the 1st year and annually after that. The prognosis of thyroglossal cyst duct carcinoma is similar to that of papillary thyroid cancer.
| Conclusion|| |
Carcinomatous transformation of ectopic thyroid elements within the thyroglossal duct is a rare entity. Surgeons should be aware of TDC in surgical planning and postoperative treatment and should include this pathology in differential diagnosis of anterior midline neck masses. Prognosis of papillary carcinoma arising in TDC is very good with only rare instances of metastases. De novo papillary carcinoma in the TDC should be differentiated from occult thyroid papillary carcinoma, which must be treated by thyroidectomy. Regular follow-up to detect any recurrence in the thyroid gland is essential, particularly in cases where the thyroid gland is not resected.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]