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         Non-Neoplastic Lesions of Thyroid

           Hypothyroidism

    • Primary causes:
      1. Congenital causes:
        1. Genetic defects in thyroid development ( FOXF1, TSH receptor mutations)
        2. Thyroid hormone resistance syndrome (THRB mutations)
    • Congenital biosynthetic defect (dyshormogenetic goiter)
    1. Thyroid agenesis
    2. Thyroid hypoplasia
    1. Iatrogenic:
      1. Drugs (lithium, iodides, aminosalicylic acid)
      2. Postablative
        • Radioiodine therapy
        • External radiation
        • Surgery
      3. Autoimmune:
        1. Hashimoto’s thyroiditis
      4. Others:
        1. Iodine deficiency
    • Secondary causes:
      1. Pituitary failure
      2. Hypothalamic failure

Thyrotoxicosis

It is a hypermetabolic condition caused by increased levels of  free circulating T3 and T4.

Causes:

    • Thyroid related causes: most common cause so often referred as hyperthyroidism
      1. Primary:
        1. Graves disease
        2. Multinodular goiter3.
        3. Neonatal thyrotoxicosis associated with maternal Graves disease4.
        4. Iodine related hyperthyroidism
    1. Secondary:
      1. Pituitary adenoma
    • Not related with hyperthyroidism:
      1. Struma ovarii
      2. Exogenous thyroxine intake
      3. Granulomatous thyroiditis

      

Comparison of  Graves disease and Hashimoto’s thyroiditis  

                 Graves disease

             Hashimoto’s thyroiditis

a. Hyperthyroidism

a. Hypothyroidism

b. Retention of lobular architecture  

b. Disturbed architecture

c. Follicular hyperplasia

c. Atrophic follicles

d. Colloid absent

d. Colloid may be present or absent

e. Vascular congestion prominent

e. Vascular congestion not prominent

f. No fibrosis

f. interlobular fibrosis

g.Thyroid stimulating immunoglobulin (TSI)

d. Anti-thyroid peroxidase (anti-TPO) and antithyrogloulin (anti-Tg)

 

                                               

   Thyroiditides

    1. Acute thyroiditis:

Cause: infection, radiation exposure

Clinical presentation: malnourished, immunocompromised children and elderly. Healthy patients with trauma. Painful enlarged gland

Gross: Normal appearing gland

Microscopy: acute inflammation with microabscess formation

    1. Granulomatous subacute thyroiditis:

Cause: viral infection, HLA association

Clinical presentation: usually in females. Hyperthyroidism. Painful

Gross: Asymmetric enlargement. Firm and poorly demarcated nodules

Microscopy: loss of follicular epithelium. Depleted colloid, granuloma, central fibrotic reaction

    1. Chronic lymphocytic thyroiditis: (Hashimoto’s thyroiditis)

Cause: autoimmune

Clinical presentation: hypothyroidism

Gross: firm, symmetrically enlarged, tan-yellow gland with interlobular fibrosis

Microscopy: small and atrophic follicles. Colloid may be present or absent. Lympho-plasmacytic infiltrate with germinal center formation. Extensive fibrosis can be seen. Apoptosis. Nuclei show clearing, enlargement and overlapping.

    1. Others: include painless/postpartum thyroiditis, palpation thyroiditis and focal non-specific thyroiditis.

 

    Fibrosing Thyroid Lesions

    • Thyroid related causes:
      1. Thyroiditis
        1. Reidel thyroiditis (Ig4 related disease)
        2. Fibrosing variant of Hashimoto’s thyroiditis
      2. Radiation fibrosis
      3. Amyloidosis associated with Medullary thyroid carcinoma
    • Systemic causes
      1. Collagen vascular disease
      2. Systemic amyloidosis

 

Pigments in Thyroid

Hemosiderin: present in macrophages

Hemochromatosis: present in follicular epithelium

Minocyclin associated coal black pigment: seen in follicular epithelial cells

                                                      

Nodular goiter

Clinically: usually euthyroid

Gross: Enlarged gland. Intact capsule. Multiple nodules with different consistency separated by normal thyroid. Colloid, calcification and fibrous bands can be seen

Microscopy: Multiple nodules with thyroid follicles of variable size and abundant colloid. Hemarrhage, fibrosis, calcification and lymphocytes can be present.

                                  Follicular Adenoma

Clinically: Euthyroid and solitary dominant nodule

Gross: Single, spherical and encapsulated lesion. Cut-surface is gray-white to red brown. 3cm on average but can be large reaching to 10cm. cystic change, hemorrhage, fibrosis and calcification is also present.

Microscopy: Encapsulated and compressing the surrounding gland . Uniform pattern throughout the nodule.  Cells show little variation in size, shape and nuclear morphology. Mitotic figures are rare.

      

Dr Saadia hafeez 

 

 

 

 

 

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