Thyroid Pathology (5/20) Flashcards
List non-neoplastic lesions of the thyroid
- Nodular goiter
- Diffuse toxic goiter (Graves’)
- Chronic lymphocytic thyroiditis
List tumors of the thyroid
- Adenoma
- Malignant (papillary, follicular, medullary, anaplastic carcinoma)
How many lobes does the thyroid have?
2
Describe the histology of the follicles
Follicles of varying sizes contain colloid and are lined by low-cuboidal to columnar epithelial cells (aka follicular cells)
What is an oncocytic cell?
- A metaplastic follicular cell
- Eosinophilic due to increased number of mitochondria
- Rounder nucleus than a follicular cells’
- Prominent nucleolus
- Seen in both benign and malignant lesions
- Also known as a Hurthle cell
What are C-Cells?
- Parafollicular cells
- Derived from neural crest
- Produce calcitonin
- Located at lateral aspect of thyroid gland
- Rarely seen in regular histology until hyperplastic (MEN2 syndromes)
- Best seen with immunostains for calcitonin
What are two types of enlargements of thyroid disease
Nodular and diffuse
What does nodular look like?
Encapsulated
- Capsule can have smooth borders (benign)
- Capsule can have irregular borders with invasion of tumor cells into surrounding thyroid or outside thyroid gland
What types of lesion architecture/growth patterns are there?
- Follicular
- Papillary
- Solid
- Trabecular
What other lesion features do we look at besides cellular ones?
- Fibrosis
- Calcification (dystrophic)
- Amyloid (distinct for medullary thyroid carcinoma)
What do we look at with tumor cell cytology?
- Cell size
- Cytoplasm (indistinct or oncocytic)
- Nuclear morphology (shape, intranuc folds (grooves), holes (inclusions))
- Nucleoli are prominent (oncocytic) or central vs eccentric
What is papillary formation?
Finger-like projections or fronds which consist of single or mult layers of hyperplastic/neoplastic epithelium centered around a core/stalk containing blood vessels and connective tissue
What kinds of nodular thyroid enlargement can there be?
- Solitary nodule which can be neoplastic/benign (more suspicious for being a neoplasm)
- Multiple nodules which are usually benign, though one may not be
Describe the two diseases in which we see diffuse thyroid enlargement
- Graves’ (diffuse toxic goiter)
2. Hashimoto’s thyroiditis (chronic lymphocytic thyroiditis)
Are diffuse thyroid enlargements usually malig or benign?
benign, rarely tumors
What is the gross pathology of Graves’?
- Symmetric and diffuse enlargement of thyroid
- Red brown cut surface
- Decreased colloid
- Increased vascularity
- Smooth capsule, no nodules
What does Graves’ look like histologically?
Hyperplasia of follicular cells (papillary hyperplasia)
Lymphocytic infiltration in stroma (autoimmunity)
–non-destructive autoimmunity–>immunoglobulins stimulate hyperplasia
Why do papillary infolds occur in graves;?
There are inc numbers of cells, usually of inc size that cannot be accommodated in the follicles in the usually way so infoldings must occur. Eventually, the hyperplastic epithelium piles up in the lumen of the follicle and develops its own fibro-vascular core (ie BVs and fibrous tissue forming center and cells attached at the periphery)
What do the follicular epithelial cells look like in graves’?
They are tall, columnar, inc in number with enlarged nuclei
What occurs in the stroma in graves’?
Inc vascularity and lymphocytic infiltration
What does Hashimotos look like grossly?
Diffusely enlarged gland (early)
Lobulated cut surface (later)
- Thyroid is symmetrically enlarged from 2-5x normal
- Thyroid capsule is smooth
- Gland is rubbery, firm and the cut surface has a lobular yellow appearance
What is Hashimotos?
Autoimmune disease in which the thyroid is destroyed by inflammatory cells
- commonly found in pts with spontaneous hypothyroidism
- also called chronic lymphocytic thyroiditis
- cells get into gland and cause enlargement
What does hashimotos look like histologically?
- Infiltration of thyroid gland by lymphocytes and plasma cells
- Follicular atrophy (not hyperplastic)
- Hurthle cell/oncocytic metaplasia (hashimoto thyroiditis leads to less colloid)
What does hashimotos look like microscopically?
- Diffuse infiltration of lymphocytes
- Formation of lymphoid germinal centers
- Follicular atrophy
- Follicular epithelium has oncocytic metaplasia
- Marked dec in colloid
What is the difference between graves and hashimotos with regards to follicular cells?
G: papillary hyperplasia
H: atrophy
What is the difference between graves and hashimotos with regards to infiltration?
G: lymphocytic infiltration in the stroma
H: infiltration by lymphocytes and plasma cells throughout the gland
What is the difference between graves and hashimotos with regards to onocyctic metaplasia
OCcurs in hashimoto, not really in graves’
How common are thyroid nodules in USA?
4-7% of general pop has them
inc in places with iodine deficiency