Thyroid Histology and Papillary Carcinoma Flashcards
What is the main function of the thyroid gland?
The thyroid gland produces thyroid hormones (T3 and T4) that regulate the basal metabolic rate of cells.
What unique histological feature makes the thyroid gland easily recognizable under the microscope?
The presence of follicles—spherical structures filled with colloid (thyroglobulin) surrounded by a single layer of follicular cells.
What is stored in the colloid of the thyroid follicles?
Thyroglobulin, a precursor that binds iodine and is used to produce thyroid hormones.
What are the two major thyroid hormones and what do they do?
Triiodothyronine (T3) and thyroxine (T4); they increase the metabolic rate of cells.
What are parafollicular (C) cells and what hormone do they produce?
Parafollicular cells are found between thyroid follicles and secrete calcitonin, which lowers blood calcium levels.
How can the activity level of follicular cells be inferred under a microscope?
Their shape—tall columnar cells are active; flat squamous cells are inactive.
What is the function of the parathyroid glands?
They secrete parathyroid hormone (PTH), which increases blood calcium levels.
What are the main cell types found in the parathyroid glands?
Chief (principal) cells that make PTH and oxyphil cells (function unknown).
How does parathyroid hormone affect calcium levels?
It increases blood calcium by stimulating osteoclasts, increasing intestinal calcium absorption, and reducing kidney calcium excretion.
How does calcitonin function compared to parathyroid hormone?
Calcitonin decreases blood calcium levels, while parathyroid hormone increases them.
What is a key diagnostic feature of papillary carcinoma in the thyroid?
Presence of true papillary structures.
Is there such a diagnosis as ‘papillary adenoma’ in the thyroid?
No, all papillary structures in the thyroid are considered malignant (papillary carcinoma).
What are psammoma bodies, and where are they commonly found?
Calcified concentric structures often found in papillary carcinomas (thyroid, breast, ovary).
What does the presence of fibrovascular cores in papillary structures suggest?
Classical histological feature of papillary carcinoma.
Do papillary thyroid carcinoma cells always have nuclear features of malignancy?
Not necessarily—malignancy can be diagnosed based on architecture alone.
What are some common nuclear features seen in papillary thyroid carcinoma?
Orphan Annie eye nuclei and nuclear pseudoinclusions.
What causes psammoma bodies to form in papillary carcinoma?
Degeneration and calcification of papillae in a concentric pattern.
Can the diagnosis of papillary carcinoma be made without seeing psammoma bodies?
Yes, psammoma bodies are common but not required for diagnosis.
