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Thyroid cancer

Last updated: August 9, 2021

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Thyroid cancer is a malignant tumor that arises from either the thyrocytes or the parafollicular cells of the thyroid gland. It is more common in women, especially between 30–50 years of age. The predominant risk factors for thyroid cancer are a history of childhood irradiation to the head and neck and a family history of thyroid cancer. Thyroid cancer typically manifests as firm to hard thyroid nodule (or nodules). Initial evaluation of all patients includes TSH assay and thyroid ultrasound. Sonographic signs of thyroid cancer include a solid, hypoechoic nodule(s) with irregular margins, microcalcifications, and evidence of local infiltration into adjacent structures or cervical lymph nodes. On thyroid scintigraphy, which should be obtained in patients with low serum TSH, a malignant nodule is typically “cold” or hypofunctional. Cytopathological analysis with FNAB is required to confirm the diagnosis. Depending on the cell of origin, thyroid cancer can be classified as papillary, follicular, medullary, or anaplastic thyroid cancer. Most thyroid cancers are treated surgically with total thyroidectomy (in some cases with hemithyroidectomy), followed by adjuvant therapy, which may include RAIA and TSH suppression therapy with L-thyroxine, radiation therapy, and chemotherapy. In advanced anaplastic carcinoma, only palliative care may be feasible. The prognosis depends on the type of thyroid cancer.

Epidemiological data refers to the US, unless otherwise specified.

References:[3]

Characteristic features of thyroid cancer [4]
Tissue of origin Carcinoma Differentiation Characteristics

Distribution

Peak incidence
Thyrocytes Papillary thyroid carcinoma

Well differentiated

  • ∼ 80% of cases [5]
  • 30–50 years of age

Follicular thyroid carcinoma

  • ∼ 10% of cases [6]
  • 40–60 years of age

Anaplastic thyroid carcinoma

Poorly differentiated

  • ∼ 1–2% of cases [7]
  • After 60 years of age
Parafollicular cells (C cells)

Medullary carcinoma

  • < 10%of cases [9]
  • 50–60 years of age

Papillary carcinoma is the most Prevalent type of thyroid cancer, it features Palpable lymph nodes, and it has the best Prognosis compared to all other types of thyroid cancer.

Thyroid carcinoma may be asymptomatic (e.g., thyroid incidentaloma) or manifest with any or all of the following clinical features: [10]

Approach [11][14]

Initial evaluation

Laboratory studies and ultrasound

Serum TSH and ultrasound should be obtained in all patients with thyroid nodules.

  • TSH: typically normal or mildly elevated [14]
  • Thyroid ultrasound: to assess for sonographic signs of thyroid malignancy [11][14]
    • Solid or mostly solid hypoechoic nodule(s)
    • Irregular margins
    • Microcalcifications within nodules
    • Nodules that are taller than wide
    • Extrathyroidal growth

Thyroid scintigraphy [11]

  • Indications
  • Contraindications: pregnant and breastfeeding women
  • Supportive findings: decreased or no radiotracer uptake (i.e., hypofunctioning or nonfunctioning nodules, referred to as cold nodules) [20]

Nodules that appear hypoechoic on thyroid ultrasound and cold on thyroid scintigraphy should increase suspicion for malignancy.

Hyperfunctioning nodules (hot nodules) are rarely malignant and typically do not require further evaluation for malignancy. [11][21]

Confirmatory tests [11][14]

Additional studies after confirmed diagnosis

Thyroid cancer tumor markers

The specific tumor markers depend on the histological type of the cancer.

Elevation of tumor markers after total thyroidectomy or RAIA indicates persistent disease, recurrence, or metastasis.

Staging [14]

Staging includes evaluation for cervical lymph node metastases in all patients and of distant metastases as needed.

Papillary thyroid cancer

Psammoma bodies

“Orphan Annie” eyes nuclei

Nuclear grooves [24]

Papi and Moma adopted Orphan Annie:” papillary thyroid cancer is histologically characterized by psammoma bodies and Orphan Annie-eye nuclei.

Follicular carcinoma

  • Uniform follicles
  • Vascular and/or capsular invasion

Medullary carcinoma

  • Ovoid cells of C cell origin and therefore without follicle development
  • Amyloid in the stroma (stains with Congo red)

Medullary carcinoma is composed of C-cells producing Calcitonin and is characterized by amyloid aCCumulation staining with Congo red.

Anaplastic thyroid carcinoma

The differential diagnoses listed here are not exhaustive.

General principles [8][14][23]

RAIA and TSH suppression therapy are not useful in the management of medullary carcinoma or anaplastic thyroid cancer. [8][23]

Surgery [14]

Surgical resection is the primary treatment for thyroid cancer. For further information on preoperative testing and complications see “Thyroid surgery.”

Total thyroidectomy

Hemithyroidectomy [14]

  • Indications
    • Small, well-differentiated thyroid carcinoma with all of the following characteristics:
      • Intrathyroidal tumors (i.e., no evidence of extrathyroidal extension)
      • No nodal or distant metastasis
      • No high-risk patient factors such as age > 45 years, history of head and neck radiation, or family history of cancer
    • Preferred option in tumors < 1 cm in size with all of the above characteristics
    • An alternative to total thyroidectomy in tumors 1–4 cm in size with all of the above characteristics
  • Contraindications
    • Intrathyroidal tumor ≥ 4 cm
    • Extrathyroidal spread
    • Distant or nodal metastasis
    • High-risk patient factors

Complications [25]

Adjuvant therapy [14]

Nonoperative management

References:[14]

Thyroid cancer

5-year survival rate

Papillary

> 90%

Follicular

50–70%

Medullary

50%

Anaplastic

5–14%

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