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For further information, see CMDT Part 26-10: Thyroid Cancer

Key Features

Essentials of Diagnosis

  • Painless swelling in region of thyroid

  • Thyroid function tests usually normal

  • Possible history of childhood irradiation to head and neck region

  • Positive thyroid fine-needle aspiration cytology

General Considerations

  • Most thyroid cancers are microscopic and indolent. Larger ones require treatment

Papillary carcinoma

  • Pure papillary or mixed papillary-follicular most common types of thyroid cancer (80%)

  • Childhood head–neck radiation or nuclear fallout exposure imparts increased lifelong risk

  • Least aggressive thyroid cancer

  • Involves both lobes in 30% of patients

  • About 80% of patients have microscopic metastases to cervical lymph nodes

Follicular carcinoma

  • Second most common thyroid cancer

  • Generally more aggressive than papillary carcinoma

  • Metastases commonly found in neck lymph nodes, bone, and lungs

Medullary thyroid carcinoma

  • 2–3% of thyroid cancers

  • One-third sporadic, one-third familial, one-third associated with multiple endocrine neoplasia type 2 (MEN 2)

  • Early metastases usually present locally; late metastases may occur in bones, lungs, adrenals, or liver

  • Peptides (eg, serotonin) can cause symptoms and serve as tumor markers

Anaplastic thyroid carcinoma

  • 2% of thyroid cancers

  • Older patient with rapidly enlarging mass in multinodular goiter

  • Most aggressive thyroid carcinoma

  • Metastasizes early to surrounding lymph nodes and distant sites

Other thyroid malignancies

  • 3% of thyroid cancers

  • Thyroid lymphomas are most commonly B cell lymphomas (50%) or mucosa-associated lymphoid tissue (MALT; 23%)

  • Other types include follicular, small lymphocytic, and Burkitt lymphoma; and Hodgkin disease

Clinical Findings

Symptoms and Signs

  • Usually presents as palpable, firm, nontender nodule

  • Larger cancers can cause neck discomfort, dysphagia, or hoarseness

  • Papillary thyroid cancer

    • Presents with palpable lymph node involvement

    • May invade the trachea and local muscles

    • Occult metastases to the lung occur in 10–15%

  • Follicular thyroid carcinoma commonly metastasizes to neck nodes, bones, and lung, but nearly every organ can be involved

  • Metastatic differentiated carcinoma may secrete enough thyroid hormone to produce thyrotoxicosis

  • Medullary carcinoma causes flushing, diarrhea, fatigue; ∼5% develop Cushing syndrome

  • Anaplastic thyroid carcinoma

    • More apt to be advanced at the time of diagnosis, presenting with signs of pressure or invasion of surrounding tissue, resulting in

      • Dysphagia

      • Hoarseness

      • Recurrent laryngeal nerve palsy

    • Patients may also have dyspnea with metastases to the lungs

  • Lymphoma usually presents as a rapidly enlarging, painful mass arising out of a multinodular or diffuse goiter due to autoimmune thyroiditis, with which it may be confused microscopically. About 20% of cases have concomitant hypothyroidism

Differential Diagnosis

  • Benign thyroid nodule

  • Subacute thyroiditis

  • Benign multinodular goiter

  • Lymphadenopathy due to other cause

  • Metastasis from head and neck cancer

  • Lymphoma

Diagnosis

Laboratory Tests

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