Causes Of Benign & Malignant Thyroid Nodules: Its Clinical Features

Causes Of Benign & Malignant Thyroid Nodules: Its Clinical Features . A circumscribed area of firmness with regular margin may be palpated as a nodule in thyroid gland. It is usually more than 1cm, as it is not possible to palpate with certainty for nodules less than this dimension. 1% to 3% of adult population has a thyroid nodule and the incidence rises with endemicity of goiter in certain geographic areas.

The size, symmetry, contour, consistency and mobility of thyroid nodule and extra-nodular thyroid tissue should be defined. Thyroid nodule may be benign or malignant.

Causes Of Benign Nodules

• Follicular adenoma
• Colloid nodule
• Cyst
• Chronic thyroiditis with nodule

In iodine deficiency areas, colloid nodules are quite common.

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They represent late stage of diffuse hyperplasia when acini are filled with colloid which is not released because stimulation by TSH has dropped.

Malignant Nodules Causes

• Differentiated carcinoma
• Un-differentiated carcinoma
• Metastatic lesion
• Lymphoma

Clinical Features Of Thyroid Nodules

Clinical history on following lines is helpful.

• Pattern of enlargement, duration and rate of growth. Short duration and rapid enlargement are consistent with neoplasm.
• Associated local symptoms e.g. pain, local or radiating to the jaw or ear, dysphagia, dyspnoea or hoarseness of voice suggests extra-thyroidal tissue involvement.
• Symptoms referable to hormonal status-
  • Malignant nodules are usually not associated with hyper to hypothyroidism.
  • Medullary carcinoma may be associated with hyper-parathyroidism and or pheochromocytoma.
    
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Physical examination: Should delineate the dimensions of thyroid nodule, whether single or multiple, regularity of its margins, consistency and fixity to adjacent structures.

• Sometimes only one nodule may be palpable.
• A solitary nodule is more likely to be malignant than several ones.
• Irregular margins, hardness and fixity are other characteristics of malignancy.
• Regional glands should be carefully evaluated.

Investigation Of Thyroid Nodules

• Fine needle aspiration biopsy (FNAC) – This method carries 85% sensitivity.
• USG- High frequency, real time, high resolution USG is most sensitive method currently available for delineating thyroid nodules. It can differentiate cystic lesion from solid lesion. However, it may not distinguish benign from malignant nodules.
• Nuclear scanning-

• Earlier scan studies with 131-I were used which delineated nodules as hot or cold.
• Cold nodule warranted suspicion of malignancy.
• Scanning today is not a front line test for evaluation of thyroid nodules.

• Hormonal evaluation- Levels of T3, T4 and TSH are done as regards functional status of thyroid nodule. In toxic, autonomous nodule T3 may be high, T4 may increase and TSH is usually sub-normal in functioning neoplasm.
• Basal and pentagastrin stimulated levels of serum calcitonin may be useful markers for medullary carcinoma.