SM157 Thyroid Pathology Flashcards
Thyroid development
First endocrine organ to develop. Starts at day 24 of gestation. Endodermal origin, from 1st pharyngeal arch. Completed by week 7 of gestation.
First aid:
Thyroid diverticulum arises from floor of primitive pharynx, descends into neck.
Connected to tongue by thyroglossal duct (normally disappears, may persist as pyramidal lobe). Foramen cecum is normal remnant of thyroglossal duct.
Most common ectopic thyroid tissue site is the tongue.
Thyroid anatomy
Highly vascular, reddish-brown gland
Two lobes connected by isthmus. Can have conical pyramidal lobe (thyroglossal duct remnant)
Two pairs of parathyroid glands lie in close proximity
Normally not palpable, nodules move with deglutition
Normal thyroid histology
Inner capsule divides the gland into lobes and lobules
Lobules composed of follicles (structural units of the gland) consisting of a simple cuboidal epithelium layer around a colloid-filled cavity
C-cells are present but rare. Synthesize and secrete calcitonin, source of medullary cancers
Thyroglossal duct cyst
Thyroglossal duct fails to atrophy, results in a spherical cyst along the midline of the neck superior to the isthmus.
Associated with the hyoid, moves with deglutition. Treatment: remove hyoid bone.
Hashimoto thyroiditis: antibodies? Histology? Clinical findings?
Thyroid peroxidase and antithyroglobulin antibodies
Hurthle cells, lymphocytic infiltrate with germinal centers
Moderately but diffusely enlarged, non-tender thyroid
Grave’s disease: antibodies? Clinical findings? Histology?
TSH-receptor stimulating antibodies
Ophthalmopathy (proptosis, EOM swelling), pretibial myxedema (dermatopathy), more connective tissue, goiter
Tall follicular cells that lack nuclear features of papillary carcinoma
Adenomatous/Colloid/Hyperplastic nodules
Goiter results from a hyperplastic adaptation to release more TSH in response to a chronic thyroid hormone deficiency
Thyroid adenoma characteristics
Discrete, solitary, non-functional, derived from follicular epithelium
Difficult to distinguish from nodules in a hyperplastic gland
Uniform follicles with intact surrounding capsule, compression of adjacent follicles
Follicular/Hurthle cell FNA findings
Type of benign adenoma.
Repetitive microfollicles and rosettes with little colloid. Eosinophilic granular cytoplasm.
Can’t distinguish carcinoma and adenoma with FNA, can distinguish adenoma and hyperplasia (adenomas are dilated from surrounding thyroid parenchyma by a capsule)
Papillary carcinoma: pathology and genetic associations?
Most common thyroid cancer
Psammoma bodies (calcifications), nucleus is elongated with finely dispersed chromatin giving the “Orphan Annie” appearance, nuclear grooves
Associated with MAP activation, either by 1) RET-PTC fusions or 2) activating BRAF mutations
Follicular carcinoma: epidemiology, gross findings, pathology?
Old women in iodine deficient places
Solitary nodules that can be infiltrative
Uniform follicles with colloid
Medullary carcinoma: cell of origin, secretion, pathology?
Parafollicular “C” cells
Secrete calcitonin
Path: highly anaplastic with variable morphologies including: polygonal cells, and spindle cells. Acellular amyloid deposits of abnormal calcitonin
Most common origins of metastasis to the thyroid?
Kidney > lung > breast
Thyroid lymphoma
Primary or secondary. Non-Hodkin’s, B cell type is most common
Most important test for diagnosis of thyroid nodules? When should you biopsy?
FNA
> 1 cm
