Anaplastic Thyroid Carcinoma
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Anaplastic Thyroid Carcinoma
📊 Epidemiology of Anaplastic Thyroid Carcinoma
| Feature | Details |
|---|---|
| Incidence | ~5% of all thyroid malignancies |
| Age group | 60–80 years (very rare before 50 years) |
| Sex | Female : Male = 3 : 2 |
| Origin | Undifferentiated carcinoma arising from follicular epithelium |
| Mortality | Very high; median survival 3–5 months |
⚠️ Etiology & Risk Factors of Anaplastic Thyroid Carcinoma
- Previous neck radiation exposure
- Pre-existing multinodular goiter
- Pre-existing differentiated thyroid carcinoma
- Iodine deficiency
- Genetic mutations
What are the genetic mutations seen in Anaplastic Thyroid Carcinoma?
🩺 Clinical Features of Anaplastic Thyroid Carcinoma
| Feature | Description |
|---|---|
| Onset | Often arises in a long-standing multinodular goiter or papillary carcinoma |
| Nature | Rapidly enlarging, painful, hard, ill-defined anterior neck mass |
| Fixity | Fixed to underlying structures |
| Pain | Common |
| Surface | Irregular, nodular |
| Consistency | Hard, woody |
| Local invasion (70%) | Muscles, trachea, esophagus, larynx, recurrent laryngeal nerve |
| Symptoms of invasion | Dyspnea, stridor, dysphagia, hoarseness, referred otalgia |
| Cervical nodes | Involved in ~80% at presentation |
| Distant metastasis | Seen in 30–50% |
What is the most common site of distant metastasis in Anaplastic thyroid carcinoma?
🚩 Painful thyroid swelling in an elderly patient → think Anaplastic carcinoma.
🧬 Staging (AJCC/UICC) of Anaplastic Thyroid Carcinoma
🚩 All anaplastic carcinomas are Stage IV at presentation.
| Stage | Description |
|---|---|
| Stage IVA | Tumor confined to thyroid |
| Stage IVB | Extrathyroidal extension (local invasion) |
| Stage IVC | Distant metastasis |
🔬 Histopathology of Anaplastic Thyroid Carcinoma
Origin: Undifferentiated tumor of follicular epithelium.
Common Histological Variants
| Type | Features |
|---|---|
| Epithelioid (Pleomorphic) | Giant cells, bizarre nuclei |
| Sarcomatoid | Spindle-shaped cells, most common |
| Others (rare) | Angiomatoid, osteoclastic, rhabdoid, lymphoepithelioma-like, carcinosarcomatoid, adenosquamous, fibrosing types |
Key Microscopic Findings
- Giant and spindle cells
- Atypical mitosis
- Extensive necrosis
- Inflammatory infiltrate
- Angio-lymphatic invasion
What is the most common histological subtype in Anaplastic Thyroid Carcinoma?
🧪 Investigations of Anaplastic Thyroid Carcinoma
| Investigation | Findings / Purpose |
|---|---|
| FNAC | Confirms undifferentiated malignant cells |
| Ultrasound Neck | Large, ill-defined, hypoechoic solid mass with extrathyroidal spread |
| Contrast enhanced CT (Neck + Mediastinum) | Heterogeneously enhancing mass, infiltrating thyroid and adjacent structures; necrosis/hemorrhage → central hypodensity |
| MRI (Neck) | For staging & local invasion |
| Chest X-ray / CT Chest | To detect lung metastasis (MC site) |
| Bone Scan | Detects osseous metastasis |
What is the Investigation of choice in Anaplastic Thyroid Carcinoma?
🏥 Treatment of Anaplastic Thyroid Carcinoma
Treatment is largely palliative, as the tumor is highly aggressive with poor prognosis.
1️⃣ Resectable Locoregional Disease
- Total thyroidectomy + central and lateral neck dissection
- Avoid extensive ablative procedures (e.g. total laryngectomy)
- Tracheostomy if airway compromised (dyspnea/stridor)
- Adjuvant therapy: External beam radiotherapy
2️⃣ Unresectable Disease
- Surgery not possible due to extensive invasion.
Treatment Options:
- Chemoradiation:
- Radiation: 60–70 Gy (hyperfractionated, 40–45 fractions / 5–6 weeks)
- Palliative doses: 20 Gy × 5 fractions (repeat in 4–6 weeks) or 30 Gy × 10 fractions
What drugs are used for chemotherapy in Anaplastic thyroid carcinoma?
💡 Anaplastic Thyroid Carcinoma is generally chemoresistant, so drugs are used mainly to enhance radiosensitivity.
3️⃣ Metastatic Disease
- Palliative therapy aimed at symptom relief and maintaining quality of life.
- Short 1–2 week course of palliative radiotherapy.
📉 Prognosis of Anaplastic Thyroid Carcinoma
| Feature | Prognostic Significance |
|---|---|
| Overall outlook | Extremely poor |
| Median survival | ~4 months |
| 5-year survival | < 10% |
| Death | Usually within 1–2 years of diagnosis |
⚠️ Even with aggressive therapy, median survival remains < 6 months.
What are the poor prognostic factors in Anaplastic Thyroid Carcinoma?
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