Thyroid Pathology Flashcards
What are the normal histological features of thyroid tissue?
round-oval follicles of various sizes lined by epithelial cells and filled with pink colloid containing thyroglobulin, thin fibrous septa with rich blood supply, and interstitial C cells (not easily seen)
How are C cells different from thyroid follicular cells?
They are neuroendocrine rather than epithelial in origin and therefore produce different kinds of cancers than thyroid tissue
What happens to normal thyroid follicular cell shape upon activation by TSH?
They get taller, scallop colloid from follicle
What are the histopathological changes in diffuse nontoxic simple goitre?
cell hyperplasia and crowding of follicles; some follicles larger than others, contain large colloid-filled cysts
What changes occur in multinodular goitre?
Cycles of hyperplasia and involution of simple goitre eventually lead to rupture and fibrosis and hyperplasia of nodules
What is toxic multinodular goitre?
If multinodular goitre progresses, these nodules can become autonomous and function without TSH, causing hyperthyroidism
What is Pemberton’s sign?
Caused by mass effect of an enlarged thyroid compressing SVC when the arms are raised above the head causing venous congestion and reddening of the skin
What are the histopathological changes in Hashimoto’s thyroiditis?
mononuclear inflammatory infiltrate (T & B lymphocytes, plasma cells, germinal centres); thyroid cells are large and blocky with abundant eosinophilic granular ctyoplasm (Hürthle cells); increased interstitial connective tissue (fibrosis and scarring from chronic inflammation)
What is the macroscopic appearance of Hashimoto’s thyroiditis?
Enlarged gland eventually becomes atrophic; cut surface is firm, tan-yellow and pale (fibrotic), somewhat nodular - cutting through an unripe pear
What is the pathological process of Hashimoto’s thyroiditis?
breakdown of tolerance to thyroid tissues causes damage: CD8+ cytotoxic T cell-mediated cytokine-mediated cell death (IFN-y, Fas/apoptosis), Abs may damage cells, TSH-blocking Abs further reduce function; cause is unknown 0 Treg abnormalities or exposure of normally sequestered Abs
What are the histopathological changes in Grave’s disease?
follicular cells are tall and more crowded; diffuse hypertrophy (increase in size) and hyperplasia (increase in numbers) - may form papillae in follicle lumen; widespread scalloping of colloid which is often paler-staining and decreased in volume; lymphocytic infiltrate
What is the macroscopic appearance of Grave’s disease?
Diffuse symmetrical enlargement (no nodules), cut surface is soft and meaty i.e. no fibrosis or scarring
What is the pathological process of Grave’s disease?
Autoimmune process targeting the TSH receptor - 3 types of antibodies: thyroid stimulating Igs (TSI) and thyroid growth-stimulating Igs both bind and stimulate the TSH receptors; TSH-binding inhibitor Igs bind and stimulate or inhibit TSH receptors - can cause hypothyroid presentation
What type of autoimmunity is Grave’s disease?
Type II antibody-mediated (B-cell) hypersensitivity
What type of autoimmunity is Hashimoto’s disease?
Type IV delayed-type (T-cell) mediated hypersensitivity
