Thyroid Histology 177 Flashcards
When during gestation does the thyroid gland develop?
day 24 of gestation
first endocrine gland to develop
What embryological structure does the thyroid gland develop from?
originates from a proliferation of endodermal epithelial cells on the median surface of the pharyngeal floor (from the first pharyngeal arch)
Describe the descent of the thyroid?
it descends and is connected to the tongue by the thyroglossal duct
becomes obliterated during weeks 7-10
What are Hurthle cells?
epithelial cells with abundant, granular cytoplasm that are rich in mitochondria and may be metaplastic or neoplastic in the thyroid
What are C-cells derived from?
derived from neural crest cells
What are the findings on fine needle aspiration biopsy of hyperplastic/adenomatous/adenomatoid nodules?
follicular/metaplastic hurthle cells and variable degenerative changes
What is the gross pathology of Hashimoto thyroiditis? Microscopic?
gross: usually diffusely enlarged
microscopic: extensive infiltration of parenchyma by a mononuclear inflammatory infiltrate of small lymphocytes, plasma cells, and germinal centers with atrophic follicles lined by Hurthle cells
What are the FNA biopsy findings of Hashimoto’s thyroiditis?
Hurthle cells in conjunction with heterogenous lymphocytes
What is the most common congenital anomaly of the thyroid?
a thyroglossal duct cyst
midline, spherical cystic mass that moves with swallowing
What is the triad of clinical findings of Graves’ disease?
diffuse hyperplasia of the thyroid, ophthalmopathy, and dermatology
What is the treatment of thyroglossal duct cysts?
removal of the cyst and part of the hyoid bone
sistrunk procedure
What genetic mutations can be associated with thyroid adenomas?
mutations of RAS or PIK3CA
What is the gross pathology of thyroid adenomas?
encapsulated masses with areas of hemorrhage, fibrosis, calcification, and cystic changes
What are the major subtypes of thyroid carcinoma?
papillary carcinoma, follicular carcinoma, anaplastic (undifferentiated) carcinoma, medullary carcinoma
What are the macroscopic and microscopic findings of papillary carciomas of the thyroid?
macroscopic: fibrosis, calcification (psammoma bodies), cystic changes
microscopic: oval to elongated shape, finely dispersed chromatin, optically clear or empty appearance (orphan annie eye nuclei), intranuclear inclusions
What genetic changes are associated with papillary carcinomas?
activation of the MAP kinase pathway
- rearrangements of RET or NTRK1
- activating point mutations in BRAF
Follicular carcinomas are more frequent in areas with iodine (sufficiency or deficiency).
Follicular carcinomas are more frequent in areas with iodine deficiency.
What are the microscopic characteristics of follicular carcinoma?
uniform cells forming small follicles containing colloid or may have nests of cells without colloid
What is the clinical course of follicular carcinoma?
slowly enlarging painless, nodules that don’t often invade lymphatics
What is the treatment for follicular carcinomas?
total thyroidectomy followed by radioactive iodine
What are non-invasive follicular thyroid neoplasm with papillary-like nuclear features?
an encapsulated follicular variant of PTC that is minimally invasive characterized by encapsulation, follicular growth pattern, and some features of papillary carcinoma
What is the clinical presentation of anaplastic carcinomas?
rapidly enlarging neck masses, aggressive, high mortality
What is the microscopic morphology of anaplastic carcinoma?
1) pleomorphic giant cells
2) spindle cells with sarcomatous appearance
3) mixed spindle and giant cells
What cells form thyroid medullary carcinomas?
C cell derived neuroendocrine neoplasms
- sometimes they secrete hormones like serotonin, ACTH, and VIP*
- can be sporadic or associated with MEN syndromes or familial tumors*
What is the microscopic morphology of medullary carcinoma?
polygonal to spindle shaped cells that can form nests, trabeculae, or follicles
acellular amyloid deposits in adjacent stroma
What types of lymphomas are associated with Hashimoto’s thyroiditis?
non-hodgkin and B cell type lymphomas
What is the most important test in the diagnosis of thyroid nodules?
fine needle aspiration biopsy (FNA)
What is this?
papillary adenocarcinoma
- atypical nuclear morphology*
- hypochromasia, nuclear grooves, intranuclear inclusions, ovoid nucleuis, “orphan annie eye” nuclei*
