Thyroglossal Duct Cyst Carcinoma
duct cyst (TDC) is the second most common neck mass in a child
occurring in 7% of the population. It's a benign cystic bump in the
middle of the neck near the hyoid bone that moves with tongue
protrusion. The diagnosis can be corroborated with ultrasound. Excision
of the cyst and duct along with the central portion of the hyoid bone
is curative (Sistrunk's procedure). A papillary carcinoma (CA) can
arise from a preexisting TDC from the thyroembryonic follicular thyroid
remnant cells. The incidence of papillary carcinoma is 1% in surgically
removed TDC. 90% of TDC carcinomas are papillary or follicular in
origin, 5% are squamous cell and the rest is anaplastic, Hurthle cell
or adenocarcinoma. Median age of diagnosis of TDC carcinoma is 40
years. TDC-CA occurs de novo arising from ectopic thyroid gland tissue.
They are not a metastasis from an occult thyroid primary and any lesion
found in the thyroid gland represents a multifocal independent primary
cancer. Females are more commonly affected. Cervical node metastasis
from papillary TDC carcinoma occurs in 10-25% of cases. After finding a
papillary carcinoma in the specimen of the excised TDC in a child there
exists controversy whether performing a total thyroidectomy or not.
Most cases are found incidentally after examining the specimen
histologically. Once the diagnosis is established an ultrasound of the
neck and thyroid gland should be performed along with FNA biopsy of any
suspicious nodule in the thyroid gland or lymph node. Genetic testing
for BRAF, N-RAS, and H-RAS should be performed. Low risk patients
should be managed with only Sistrunk procedure and include those with
less than 45 years of age, small tumors (< 1 cm), classic histology,
no extracapsular spread, no vascular invasion, negative margins, no
nodal or distant metastasis and a normal thyroid gland and neck by
imaging studies. Without these criteria they are categorized as high
risk and managed with total thyroidectomy with or without lymph node
dissection if they are found to be FNA-positive, and radioiodine
ablation therapy. Long-term follow-up is mandatory after primary
Sistrunk procedure without total thyroidectomy. Prognosis of TDC
carcinoma is excellent with five ad 10-year overall survivals of 100%
and 96% respectively.
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