Thyroid Neoplasms - الأهلية

Thyroid Neoplasms

• Thyroid neoplasms are classified as either benign or malignant.
• Benign neoplasms: Follicular adenoma.
• Malignant neoplasms are classified according to the Dunhill classification.

Malignant Neoplasms Classification

• Primary Malignant Neoplasms:
  • Originate from different thyroid tissues.
  • Exhibit varying degrees of differentiation.
  • Include different types of carcinoma with specific distribution percentages:
    • Papillary thyroid carcinoma (60%).
    • Follicular thyroid carcinoma (17%).
    • Papillofollicular carcinoma, which behaves like papillary carcinoma.
    • Hurthle cell carcinoma, which behaves like follicular carcinoma.
    • Anaplastic thyroid carcinoma (13%).
    • Medullary carcinoma (6%).
    • Malignant Lymphoma (4%).
• Secondary thyroid neoplasms are metastatic but not common.

Follicular Adenoma (Benign)

• Clinically presents as solitary nodules and requires histological examination for differential diagnosis from follicular carcinoma.
• Angio capsular invasion:
  • Absent in adenoma.
  • Present in follicular carcinoma.
• Types of follicular adenoma:
  • Colloid: commonest type, no potential for microinvasion.
  • Fetal (microfollicular): has potential for microinvasion.
  • Embryonal (atypical): has potential for microinvasion.
  • Hurthlecell: has potential for microinvasion.
• Treatment is surgical excision via hemithyroidectomy, involving a lobectomy of the affected side plus isthmectomy.

Differentiated Thyroid Carcinoma (Malignant)

• Origin: Derived from follicular cells.
• Incidence: Accounts for 90% of thyroid cancers.
• Types:
  • Papillary.
  • Follicular.
  • Hurthle cell carcinoma.

Papillary Carcinoma

• Incidence: 70-80%, the most common.
• Age: Typically occurs in young individuals (20-40 years).
• Sex: More common in females.
• Etiology: Associated with radiation exposure or radioactive iodine therapy.
• Woolner Classification:
  • Occult (30%): Small tumor (<1 cm), presents with positive cervical lymph nodes.
  • Intrathyroidal (50%): Presents as a solitary thyroid nodule (STN).
  • Extrathyroidal (15%): Presents as extra capsular spread or multiple foci in the thyroid gland.
• Microscopic Features:
  • Shows cystic spaces, papillary projections with psammoma bodies.
  • exhibits malignant cells with Orphan Annie eye nuclei, nuclear grooves, and nuclear pseudo-inclusions.
  • Commonly multicentric.
• Spread: Primarily through lymphatics.
• Prognosis: Excellent, slowly progressive, less aggressive, curable malignancy.

Follicular Carcinoma

• Incidence: 10-15%.
• Age: Middle-aged individuals (30-50 years).
• Sex: More common in females (2:1 ratio).
• Etiology: Can arise de novo or from a pre-existing multinodular goiter.
• Woolner Classification:
  • Minimally Invasive (50%): Well encapsulated, presents as STN.
  • Highly Invasive (50%): Presents as multiple foci within the thyroid gland.
• Microscopic Features:
  • Consists of follicular cells with variable differentiation degrees.
  • Diagnosis depends on capsular and vascular invasion.
• Lymph node spread in Hurthle cell variant.
• Spread: Mainly through the bloodstream, commonly to bones, lungs, and liver.
• Prognosis: Good, but is an aggressive tumor.

Anaplastic (Undifferentiated) Carcinoma

• Incidence: 1%.
• Age: Older individuals (50+ years).
• Sex: More common in females.
• Presents as a bulky irregular mass invading through the gland capsule, encircle the cervical structures and extends down to the mediastinum.
• Three forms exist: spindle cell type, small cell type, and giant cell type.
• Spread: Occurs through lymphatics, blood, and direct invasion.
• Prognosis: Very poor. Most patients die within the first 2 years.

Medullary Carcinoma

• Incidence: Uncommon, accounting for 5% of thyroid malignancies.
• Types:
  • Sporadic: Occurs in the 5th-6th decade, more common in females, usually solitary and unifocal.
  • MCT with MEN II Syndrome : Affects a younger age group with bilateral, multifocal/multicentric lesions.
  • Familial Non-MEN MCT: Occurs in the 4th-5th decade, commonly multicentric, autosomal dominant in chromosome 10.
• Macroscopic Features:
  • Color: Grey-white, well-demarcated.
  • Size: Varies considerably.
• Microscopic Features:
  • Derived from parafollicular C-cells derived from the neural crest.
  • amyloid stroma
• Produces calcitonin.
• Spread: Nodal.
• Hormonal: Not TSH-dependent and does not take up radioactive iodine.

Clinical Presentation of Thyroid Carcinoma Classifications:

• Carcinoma on Preexisting Multinodular Goiter (Bilateral Carcinoma):
  • Occurs in middle-aged & elderly females.
  • Presents with recent increase in goiter size, hoarseness, persistent cough, dyspnea, and occasional dysphagia.
  • Presence of excessive induration, fixity to surrounding structures, and enlarged cervical lymph nodes are suspicious.
• Symptomless STN in Healthy Gland of Young Male Child (Carcinoma de Novo - Unilateral):
  • A symptomless STN in a child or adolescent is considered carcinoma unless proven otherwise.
  • Histologically, such tumors are often papillary carcinoma.
• Lump in the Neck with Occult Primary Tumors on the Thyroid (Occult Carcinoma - Unilateral):
  • Occurs predominantly in young or middle-aged males.
  • Presents with a unilateral lump in the neck without a history of sore throat or tuberculosis.
  • The thyroid is not enlarged, but LNs are found on one side of the neck (enlarged, matted, firm, not tender.)
• Investigation:
  • Biopsy of LNs: Shows thyroid tissue with papillary carcinoma.
• Rapidly Increasing Swelling of the Thyroid with Hoarseness of Voice and Dyspnea (Diffuse or Bilateral Carcinoma de Novo):
  • Occurs in elderly males or females.
  • Thyroid gland shows swelling with a diffuse margin and fixed to the infrahyoid muscles & trachea.
  • Cervical LNs are enlarged, hard, irregular, and not tender.
• Histopathology typically shows anaplastic carcinoma.

Complications Presentation of Thyroid Carcinoma

• Local Spread:
  • More common in anaplastic types.
  • First to remaining thyroid parts & then trachea, esophagus, and surrounding tissues.
• Lymphatic Spread:
  • More common in papillary types.
  • Pretracheal, prelaryngeal, internal jugular, posterior triangle, and upper mediastinal LNs
• Hematogenous Spread:
  • More common in follicular types.
  • To lungs and bone.
• Pressure Manifestations:
  • Trachea: Dyspnea.
  • Esophagus: Dysphagia.
  • RLN: Hoarseness of voice.

Investigations for Thyroid Neoplasms

• Laboratory Tests:
  • Thyroid Function Tests: Measures Free T3, Free T4 and TSH levels.
  • Thyroid Antibodies: May be elevated in carcinomas.
  • Tumor Markers: Measures serum thyroglobulin and calcitonin (in medullary carcinoma).
• Imaging:
  • Neck US: Gives good anatomical images of the thyroid and surrounding structures.
    • It helps in identify nodules (number, size, vascularity, and echogenicity) and neck lymph nodes.
    • It helps in USG-guided FNAC and detect recurrent cases and helps differentiate between solid and cystic nature, and single or multiple nodules
    • help differentiate benign and malignant lesions.
  • Plain X-ray (of Limited Value):
    • Indicated in calcifications, pulmonary metastases, tracheal shift, or enlargement.
• Isotope Scan:
  • Done for nodules appearing solid in US.
  • Cold nodules (8-25% chance of malignancy): Thyroiditis, Cyst Fibrosis, Non functioning adenoma, Multinodular goitre, Malignancy
  • Hot nodules (malignancy rare): Functioning adenoma, Thyroiditis.
• Pathological Investigation: -FNAC in most thyroid diseases for pathological diagnosis to confirm thyroid disease
  • Useful in: Papillary carcinoma, medullary carcinoma, anaplastic carcinoma, lymphomas, colloid nodules, and thyroiditis.
  • Diagnostic accuracy 95% sensitivity and 85% specificity.
  • FNAC is not reliable at present in follicular carcinoma because angio-capsular invasion couldn’t be evaluated. -Tru-cut is for huge tumors and complications include hemorrhage, pain, and injury for trachea/nerves.
  • Open biopsy to confirm hemithyroidectomy.
• Endoscopic investigations:
  • Direct and indirect laryngoscopy for visualization of vocal cords, 3% asymptomatic cord paralysis.
• Metastatic Workup: -Includes Bone survey or scan, abdominal US, barium swallow for esophagus infiltration, and angiography in SVC obstruction.