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KAREN H.CALHOUNMDRONALD B.KUPPERSMITHMD
For papillary carcinoma in a thyroglossal duct remnant, complete wide excision of the remnant is adequate treatment.
Thyroglossal duct remnants (TGDRs) result from aberrant embryological development of the thyroid gland. During the fourth week of fetal development, the thyroid anlage arises from epithelium located in the floor of the pharyngeal gut and descends as a bilobed diverticulum. During its descent, the thyroid gland remains connected to the base of the tongue by the thyroglossal duct, which involutes as the thyroid reaches its final position in the neck by the eighth week of gestation. Persistence of this embryonic duct results in TGDRs.
These remnants, most typically cysts, occur in an equal sex distribution and may occur anywhere along the embryological route of descent of the thyroid gland in the following frequency: 2% intralingual, 24% suprahyoid, 60% between the hyoid and thyroid cartilage, and 13% substernal.1 Approximately 31% of TGDRs occur in patients before age 10 years, 20% in the second decade, 14% in the third decade, and 35% after age 30 years.1 Ectopic thyroid tissue occurs in 62% of TGDRs and is subject to the same disease processes as the thyroid gland itself.
Edmund A. Pribitkin, MD
Owen and Ingelby2 authored the first English-language report of papillary thyroid carcinoma in a TGDR in 1927. Carcinoma occurs in fewer than 1% of TGDRs.3 There is a female sex predilection, and the mean age of patients lies in the fourth decade, with age at presentation ranging from 1 to 82 years. The most common histologic subtype is papillary carcinoma, occurring in over 90% of cases including mixed papillary/follicular forms. Papillary carcinomas may be confined to the TGDR or may invade strap muscles. The incidence of cervical metastasis is low, estimated at 8%.3 Squamous cell carcinoma accounts for 5% of cases and has the worst prognosis. There have been no reports of medullary carcinoma arising from the parafollicular cells of the ultimobranchial body.
Oren Friedman, MD
The need for total thyroidectomy in patients with papillary thyroglossal duct carcinoma (TGDCa) remains a controversial issue. Many investigators argue that complete excision of the remnant via a Sistrunk procedure is adequate treatment, especially if the carcinomatous focus is small and the margins are free of tumor. Others advocate total thyroidectomy, radioactive iodine ablation, and thyroid hormone replacement in addition to complete excision.
Most investigators believe that papillary thyroid carcinomas arise de novo from the TGDRs rather than via metastatic spread from the thyroid gland. Indeed, ectopic thyroid rests have been identified in 62% of TGDR specimens.4 Histologically normal ectopic thyroid follicles are also commonly found in TGDRs containing papillary carcinoma. Although the rates of occult papillary thyroid carcinoma vary among different ethnic and demographic groups, the most commonly cited 11% incidence of unsuspected thyroid carcinoma found in patients with TGDCa who have undergone thyroidectomy falls within the 0.45% to 36% incidence of occult thyroid carcinoma discovered in cadaveric thyroid tissue at autopsy.5 Synchronous papillary carcinomas in a TGDR and the thyroid gland, therefore, represent multifocal tumor rather than metastatic spread. Moreover, the absence of medullary carcinoma and the differing relative incidences of papillary, follicular, and squamous cell carcinoma in thyroid vs TGDR tissue support a de novo theory of origin. The criteria for unequivocal diagnosis of primary TGDCa (as opposed to a cystic lymph node metastasis) include the presence of an epithelial lining and ectopic thyroid nests within the specimen in a patient with a clinically normal thyroid gland.6
Given an unequivocal diagnosis of primary papillary TGDCa without evidence of metastasis or tumor invasion of the cyst wall, Kristensen et al7 recommended complete wide excision of the remnant (Sistrunk procedure) followed by thyroid suppression. The cure rate for TGDCa treated in this fashion is over 95%.8 Performance of total thyroidectomy to facilitate nuclear imaging studies and radioactive iodine ablation is not warranted. The incidence of cervical metastasis from TGDCa is far lower than that noted with papillary carcinoma of the thyroid gland, and death due to papillary TGDCa is rare.3 Moreover, the potential for serious complications from thyroidectomy (including a 3%-5% incidence of hypocalcemia and a 1%-2% incidence of recurrent laryngeal nerve injury) argues against further surgery.
Papillary TGDCa may represent metastasis from an occult primary carcinoma of the thyroid gland via the thyroglossal duct itself. Although numerous series cite an 11% incidence of unsuspected thyroid carcinoma in patients with TGDCa who underwent thyroidectomy,5,9 LiVolsi et al10 noted a 27% incidence of malignancy in the thyroid gland proper. Papillary thyroid carcinoma may metastasize without a lesion being clinically detected in the gland itself. Consequently, total thyroidectomy is recommended followed by postoperative radioactive iodine therapy and thyroid hormone replacement.
Even given an unequivocal diagnosis of primary papillary TGDCa without evidence of metastasis or tumor invasion of the cyst wall, total thyroidectomy is warranted for reasons of long-term surveillance. The 27% incidence of occult thyroid gland carcinoma6 and the older age of patients with TGDCa supports close follow-up. Papillary TGDCa has also been shown to produce cervical metastases in the absence of associated foci of carcinoma within the thyroid gland. Moreover, distant metastases have also been described in up to 1.3% of patients with papillary TGDCa.11 The presence of the thyroid gland invalidates diagnostic nuclear imaging and diminishes the diagnostic value and accuracy of serial thyroglobulin levels. Given the long natural history of papillary thyroid carcinoma, the actual cure rate for patients undergoing treatment for TGDCa with complete wide excision followed by thyroid suppression is likely less than 95%. Furthermore, although hypocalcemia and recurrent laryngeal nerve injury can occur as a result of thyroid surgery, Kennedy et al12 maintain that the low incidence of these complications recorded by surgeons trained in contemporary thyroid surgery represents an acceptable risk in the management of papillary TGDCa.
The initial evaluation of a patient presenting with a suspected TGDR should include ultrasonography of the neck to confirm the diagnosis and establish the location of the thyroid gland. Fine needle aspiration (FNA) may be performed to further evaluate the TGDR. If the diagnosis of a TGDCa is suggested by FNA findings, magnetic resonance imaging with gadolinium is performed to evaluate the neck for local invasion, cervical metastasis, and the presence of lesions within the thyroid gland itself. Wide complete excision of the TGDCa via the Sistrunk procedure, with microscopic frozen section used to confirm the diagnosis of papillary carcinoma, is recommended for patients with papillary carcinoma confined to the TGDR. In the absence of positive histologic margins, cyst wall invasion, metastatic spread, or lesions within the thyroid gland, surgical treatment is considered complete. Patients are maintained on a regimen of thyroid hormone to suppress the secretion of thyrotropin and undergo yearly follow-up.
Exceptions to this general practice include patients at high risk for thyroid malignancy, including those receiving low-dose childhood neck irradiation and those with TGDCa tumors larger than 1.5 cm. In these patients, total thyroidectomy with postoperative radioactive iodine ablation and thyroid hormone replacement is recommended. The presence of lesions within the thyroid gland as indicated by preoperative imaging or surgical findings also warrants total thyroidectomy in addition to complete excision of the TGDCa. Evidence of local invasion or cervical metastasis as indicated by preoperative imaging or surgical findings warrants total thyroidectomy and cervical lymph node dissection in addition to complete wide excision of the TGDCa. Postoperatively, such patients are treated with radioactive iodine ablation and thyroid hormone replacement. Should papillary TGDCa be discovered only after permanent histologic evaluation, magnetic resonance imaging is performed and management concluded as described above.
Accepted for publication November 5, 2001.
We would like to thank Dave A. Opperman, MD, for his assistance in preparing the manuscript.
Corresponding author and reprints: Edmund A. Pribitkin, MD, Department of Otolaryngology–Head and Neck Surgery, Thomas Jefferson University, 925 Chestnut St, Sixth Floor, Philadelphia, PA 19107 (e-mail: Edmund.Pribitkin@mail.tju.edu).
Pribitkin EA, Friedman O. Papillary Carcinoma in a Thyroglossal Duct Remnant. Arch Otolaryngol Head Neck Surg. 2002;128(4):461–462. doi:10.1001/archotol.128.4.461
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