Thyroid Cancer

smart doctor on

 Thyroid Cancer  

Definition

Thyroid cancer is a malignant tumor that arises from cells of the thyroid gland:

  • Thyrocytes (follicular cells): give rise to papillary, follicular, and anaplastic thyroid cancers.

  • Parafollicular cells (C cells): give rise to medullary thyroid cancer.

Epidemiology

  • Incidence: ~13.5 new cases per 100,000/year (USA data).

  • Sex:

    • Differentiated cancers (papillary & follicular): more common in women (3:1).

    • Poorly differentiated (medullary & anaplastic): occur equally in men and women.

  • Age:

    • Papillary: 30–50 yrs

    • Follicular: 40–60 yrs

    • Medullary: 50–60 yrs

    • Anaplastic: >60 yrs

Explanation: Hormonal influences and radiation sensitivity make younger women more prone to differentiated thyroid cancers, while aggressive cancers (like anaplastic) usually appear in older patients.

Risk Factors

  • Radiation exposure: especially in childhood (e.g., neck radiation for tonsils, acne treatments in the past).

  • Genetics:

    • Medullary: RET gene mutations (MEN2 syndrome).

    • Papillary: RET/PTC rearrangements, BRAF mutation.

    • Follicular: RAS or PAX8-PPARγ mutation.

    • Anaplastic: TP53 mutation.

  • Family history: MEN2 or differentiated thyroid cancer.

Clinical Features

  • Most common sign: thyroid nodule that is firm, hard, and non-tender.

  • Red flags:

    • Hoarseness (vocal cord involvement).

    • Dysphagia or dyspnea (compression).

    • Fixed nodule, not moving freely.

    • Painless cervical lymphadenopathy (especially in papillary).

  • Paraneoplastic features (medullary carcinoma): diarrhea, flushing (due to calcitonin secretion).

  • Metastasis signs:

    • Follicular → lungs & bone (bone pain, fractures).

    • Anaplastic → rapid local growth, compression, systemic spread.

Explanation: Most thyroid nodules are benign. But when a nodule is fixed, hard, associated with lymphadenopathy, or compressive symptoms → malignancy is suspected.

Diagnosis

  1. First-line tests:

    • TSH level (low TSH → do scintigraphy).

    • Thyroid ultrasound → look for suspicious features:

      • Solid, hypoechoic nodule

      • Irregular margins

      • Microcalcifications

      • Taller-than-wide shape

      • Extrathyroidal extension

  2. Scintigraphy:

    • Cold nodule = ↓ uptake → higher risk of malignancy.

    • Hot nodule = ↑ uptake → usually benign.

  3. Fine Needle Aspiration Cytology (FNAC): confirms malignancy.

  4. Tumor markers:

    • Papillary & Follicular → thyroglobulin (Tg).

    • Medullary → calcitonin & CEA.

  5. Staging:

    • Neck US for lymph nodes.

    • CT, MRI, or bone scan for distant spread.

Pathology — Major Types

1. Papillary carcinoma (80%)

  • Histology:

    • Psammoma bodies (concentric calcifications).

    • “Orphan Annie-eye” nuclei (clear, empty-looking).

    • Nuclear grooves.

  • Spread: lymphatic → cervical nodes.

  • Prognosis: excellent (>90% 5-year survival).

2. Follicular carcinoma (10%)

  • Histology: uniform follicles with vascular/capsular invasion.

  • Spread: hematogenous → lungs, bone.

  • Prognosis: good (50–70% 5-year survival).

3. Medullary carcinoma (<10%)

  • Origin: C cells → calcitonin production.

  • Histology: amyloid deposition (Congo red stain).

  • Genetics: associated with MEN2 (RET mutation).

  • Symptoms: flushing, diarrhea.

  • Prognosis: moderate (~50% 5-year survival).

4. Anaplastic carcinoma (1–2%)

  • Poorly differentiated, giant cells, necrosis.

  • Very aggressive, rapidly fatal.

  • Symptoms: neck mass with dysphagia, dyspnea.

  • Prognosis: very poor (5–14% survival).

Treatment

  1. Surgery (mainstay):

    • Total thyroidectomy: for most cancers ≥1 cm, extrathyroidal spread, or high-risk patients.

    • Hemithyroidectomy: for very small, low-risk cancers (<1 cm).

    • Neck dissection if lymph node spread.

  2. Adjuvant therapy:

    • Radioactive iodine ablation (RAIA): destroys residual thyroid tissue (only for papillary & follicular).

    • TSH suppression therapy (L-thyroxine): prevents stimulation of residual cancer cells.

    • External beam radiation or chemotherapy: for unresectable or advanced disease.

  3. Special cases:

    • Medullary carcinoma: surgery + lymph node dissection (no RAIA benefit).

    • Anaplastic carcinoma: usually unresectable → palliative care.

Prognosis

  • Papillary: excellent (>90% survival).

  • Follicular: good (50–70%).

  • Medullary: moderate (~50%).

  • Anaplastic: very poor (5–14%).

Explanation: Differentiated cancers (papillary & follicular) have excellent outcomes because they retain thyroid cell functions and respond to iodine therapy. Medullary is less responsive, and anaplastic is almost untreatable.

✅ In short:

  • If you see a thyroid nodule, start with TSH + ultrasound.

  • Cold, solid, irregular nodules = suspicious → FNAC.

  • Papillary = most common, best prognosis.

  • Anaplastic = worst prognosis.

  • Treatment = surgery + RAIA (if differentiated).

Comments

Post a Comment