Address for correspondence: Dr Sushmita Bhatnagar, 56/B, Venus Apartments, Worli Sea Face, Worli, Mumbai 400018.
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Comparative Analysis

The salient features of malignancies of thyroid in children are that all children, especially those who are < 10 years of age at presentation with thyroid nodules must be investigated thoroughly and a histopathological diagnosis established rapidly so that appropriate treatment is instituted at the earliest. An attempt is made here to provide a comparison between the adult and the pediatric thyroid malignancies with a view of improved understanding of the lesion (Table 1).

There are not many diagnostic modalities to differentiate between benign and malignant thyroid nodule (as depicted in Table 2). A baseline ultrasonography and a rapid histopathological evaluation by a Fine Needle Aspiration Biopsy (FNAB) or rarely open surgical biopsy (depending on the size of the lesion) is most essential.

The most widely accepted treatment modality is surgical excision of the lesion with excision of grossly involved lymphatic system, though a radical neck dissection is not recommended by all authors.

TABLE 1 : Comparison of features between adult and pediatric Thyroid malignancies

Features	Child	Adult
Age (most common)	Adolescent	3rd & 4th decades of life
Gender differentiation	Almost equal in younger children, but girls between 15-20 years are affected 3 times more than boys (3)	Women 4 times more likely (female hormones may be causative) (4)
Occurrence	Rare	Not as rare
Types	Papillary, follicular, medullary, anaplastic	Same
Most common type of malignancy	Papillary	Papillary
Most common presentation	Asymptomatic thyroid nodule	Usually asymptomatic, but malignant nodules often present with pain, tenderness, compression of respiratory tract, dysphagia, inappropriate fixation of the neck
Incidence of malignancy in solitary thyroid nodule	20-73% (5,6,7)	5-10% (4)
Overall incidence of thyroid cancers	5%	95%
Risk of malignancy in thyroid nodule	4 times more i.e about 26%	Risk of malignancy in a thyroid nodule is less i.e. about 5%
Extent of disease at presentation	70% have extensive regional node involvement, 10-20% have distant metastases	30% have regional lymph node involvement 5-10% have distant metastases
Behavior of papillary nodule	More aggressive	Less aggressive
Prognosis	Better even with extensive disease, especially Papillary Thyroid Carcinoma (PTC)	Not good with extensive disease
Thyroid malignancy in infancy	Medullary Carcinoma, associated with Multiple Endocrine Neoplasia 2B (MEN 2B)	-
Most common site of Metastases	Lungs	Lungs and bone
Incidence of bone metastases	< 5% (3)	>40% (variable reports in different series) (4)
Mortality rates	< 10% (3)	Variable, increase significantly with extensive disease
Risk factors	Exposure to radioactive iodine, Follicular adenoma, Autoimmune thyroiditis Iodine deficiency Radiation therapy for other cancers Congenital hypothyroidism Thyroglossal duct cyst (rare)	Radiation exposure Low iodine diet (follicular and anaplastic carcinomas) Age - <30 and >60 years Nodule in a male Familial adenomatous polyposis (Gardner's syndrome) Hashimoto's thyroiditis
Vocal cord paralysis	Rarely seen	More commonly seen
Family history of thyroid cancer	25%	Not ascertained, usually seen in Medullary carcinoma or in MEN 2B
Prognosis	NOT DEPENDANT ON Stage of disease, extensive lymph node involvement, degree of invasion,	DEPENDANT ON Age/sex of the patient, Size of the tumor > 4 cm, stage of the disease, extent of local invasion
Genetic influences	Ret and PTC3 oncogene - tumor more aggressive, faster growing, less differentiated Ret and PTC1 oncogene - tumor slower growing, and with more benign characteristics.	Similar for Medullary carcinoma of thyroid (MCT)