Thyroid Cancer

Key Features

Essentials of Diagnosis

• Painless swelling in region of thyroid

• Thyroid function tests are usually normal

• Types of thyroid cancer

  • Differentiated thyroid carcinomas: papillary and follicular

  • Medullary thyroid carcinoma

  • Anaplastic thyroid carcinoma

• 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

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