Pathology of thyroid 2
Dr: Salah Ahmed
Thyroiditis
- inflammation of the thyroid gland, includes a group of disorders characterized by
some form of thyroid inflammation and thyroid dysfunction
1- Chronic Lymphocytic (Hashimoto) Thyroiditis:
- is the most common cause of hypothyroidism in areas with sufficient iodine
- is characterized by gradual thyroid failure because of autoimmune destruction of
the gland
- common between 45 and 65 years of age and is more common in women than in
men ( 10 : 1 to 20 : 1)
Pathogenesis:
- It is an autoimmune disease in which the immune system reacts against different
thyroid antigens with progressive destruction of thyroid epithelial cells (thyrocytes),
which are gradually replaced by mononuclear cell infiltration and fibrosis
- sensitization of CD4+ T-helper cells to thyroid antigens (initiating event)
- thyrocytes destruction and death, by different mechanisms:
1-cytokine-mediated thyrocytes death: reaction of CD4+ T cells to thyroid antigens,
producing cytokines (IFN-γ) which promote inflammation and activate macrophages
- injury to the thyroid by the toxic products of inflammatory cells
2- CD8+ cytotoxic T-cell-mediated thyrocytes death: CD8+ cytotoxic T cells recognize
antigens on thyrocytes and kill these cells
3- Binding of antithyroid antibodies followed by antibody-dependent cell-mediated
cytotoxicity by natural killer (NK) cells
- genetic predisposition:
1- it occurs with increased frequency in first-degree relatives, and unaffected
family members often have circulating thyroid autoantibodies
2- Association studies have reported linkage between HLA-DR3 and HLA-DR5
alleles and Hashimoto thyroiditis, but the associations are generally weak
Morphology:
- Grossly: the thyroid is usually diffusely and symmetrically enlarged
-The cut surface is pale, gray-tan, firm (LN like)
- Microscopic examination: 1- widespread infiltration of the parenchyma by a
mononuclear cells containing small lymphocytes, plasma
cells with well-developed germinal centers
2- The thyroid follicles are atrophic
3- Less commonly, the thyroid is small and atrophic as a
result of more extensive fibrosis (fibrosing variant)
Clinical Features:
- painless enlargement of thyroid, usually with hypothyroidism manifestation
- it may be preceded by transient thyrotoxicosis (disruption of thyroid follicles
("hashitoxicosis")
- Lab: - TFT: T4 and T3 levels decreased with compensatory increase in TSH
- the diagnosis based on histopathological examination of thyroid excisional biopsy
Symmetrical enlargement, pale or gray-tan cut surface
Mononuclear cell infiltration with germinal center
- patients with Hashimoto thyroiditis often have other autoimmune diseases and are
at increased risk for the development of B-cell non-Hodgkin lymphomas
2- Subacute Granulomatous (de Quervain) Thyroiditis:
- is much less common than is Hashimoto disease
- most common between the ages of 30 and 50 years, more frequently in women
Pathogenesis:
- is believed to be caused by a viral infection or a postviral inflammatory process.
- The majority of patients have a history of an upper respiratory infection just before
the onset of thyroiditis
Morphology:
- grossly: the gland is firm, unilaterally or bilaterally enlarged
- microscopically: there is disruption of thyroid follicles, with extravasation of colloid
leading to a neutrophils infiltration, which replaced over time by lymphocytes, plasma
cells, and macrophages and also giant cells
Clinical Features:
- characterized by pain in the neck (particularly with swallowing), fever, malaise, and
variable enlargement of the thyroid, hyperthyroidism manifestation
- Thyroid function test: increase in T3, T4 (disruption of follicles and hormone release
- The leukocyte count and ESR are elevated
- The condition is typically self-limited, with most patients returning to a euthyroid
state within 6 to 8 weeks.
Disruption of follicles with inflammatory cells infiltration
3- Subacute Lymphocytic Thyroiditis :
- is also known as "silent" or "painless" thyroiditis
- often occurs following pregnancy (postpartum thyroiditis)
- It commonly affects middle-aged women
Pathogenesis: The disease is most likely autoimmune in etiology, because circulating
antithyroid antibodies are found in the majority of patients
Morphology: - mild symmetric enlargement of thyroid
- lymphocytic infiltration microscopically
Clinical manifestation: - patients presented with painless neck mass or features of
hyperthyroidism (secondary to thyroid tissue damage), followed by return to a
euthyroid state within a few months
- In a minority of affected individuals the condition eventually progresses to
hypothyroidism
4- Riedel thyroiditis:
- a rare disorder of unknown etiology
- is characterized by extensive fibrosis involving the thyroid and contiguous neck
structures.
- patients presented with a hard and fixed thyroid mass clinically
-The presence of circulating antithyroid antibodies in most patients suggests an
autoimmune etiology
5- Palpation thyroiditis:
- caused by vigorous clinical palpation of the thyroid gland, results in multifocal
follicular disruption with chronic inflammatory cells infiltration and occasional giantcell formation
- the abnormalities of thyroid function are not present
- usually an incidental finding in specimens resected for other reasons.
Riedel
Thank you