Ch. 10 - Thyroid Flashcards
What percentage of adults have thyroid nodules? What proportion of nodules are malignant?
5% have palpable, >50% have nonpalpable nodules. Of these, <5% are malignant.
What risk of neoplasm is conferred by “hot” nodularity? How can this be assessed?
Hot nodules are almost never malignant and should not be FNA’d. Evidenced by decreased serum TSH.
What size criteria are used for thyroid nodule FNA eligibility? Any other features?
1cm; may biopsy smaller if suspicious-looking (microcalcifications).
What are the complications of FNA of thyroid?
Hematoma (transient), infarction (rare), needle tract seeding (almost never)
What are the criteria for specimen adequacy in thyroid FNA?
- Presence of colloid
- At least 6 clusters of at least 10 follicular cells
- Any specific diagnosis
What are the 6 categories of Bethesda thyroid reporting, their respective risk of malignancy, and their clinical consequence?
Unsatisfactory (1-5%, rebiopsy) Benign (1-3%, follow) AUS/FLUS (5-15%, rebiopsy) Suspicious for FN (15-30%, resect) Suspicious for malignancy (65%, resect) Malignant (90%, resect).
In general, what features favor malignancy on thyroid FNA?
Microfollicles, architectural atypia (noncohesiveness), papillae, pseudoinclusions & grooves. Psammoma bodies not so much.
What thyroidal conditions may exhibit multinucleated giant cells?
Acute thyroiditis, granulomatous disease
Cystic degeneration
PTC
Anaplastic carcinoma
What is the pathophysiology of multinodular goiter?
Thyroid-deficient state selects for hyperplastic follicular cells, resulting in multinodularity.
What defines follicular adenoma?
Solitary nodule composed of follicular cells that are “morphologically distinct from surrounding gland” and does not exhibit invasion.
What does the diagnosis of “benign follicular nodule” entail?
Could be MNG or follicular adenoma (indistinguishable). Used to indicate a benign lesion.
Describe the cytology of a benign follicular nodule.
Macrofollicles with colloid and low cellularity. May have some Hurthle cells, cyst lining cells with macrophages. A little atypia is okay.
Describe the cytology of Hashimoto’s thyroiditis.
Very cellular with mixed lymphoid infiltrate including dendritic cells and TBMs. Look for tangles (germinal centers). Hurthle cells are common. Colloid is scant.
Describe the cytology of subacute (de Quervain) thyroiditis.
Multinucleated giant cells and rare granulomas (reniform/boomerang histiocytes) and lymphocytes.
Describe the cytology of Riedel’s thyroiditis.
Usually a dry aspirate.
What role does FNA play in thyroiditis?
Not recommended (or even needed) for diagnosis; only to rule out malignant lesions occurring in context of thyroiditis.
What is “black thyroid”?
Dark brown pigmentation of thyroid due to tetracycline (eg. minocycline) use.
Describe the cytologic features of radiation changes. How can it be distinguished from carcinoma?
Sheets of enlarged cells with high N:C, Hurthle cell change, cytoplasmic vacuolization, and marked nuclear atypia. However, microfollicles are uncommon.
What role does FNA play for follicular neoplasms?
It is a SCREENING tool, not a diagnostic tool, and can only recommend excision for final diagnosis.
What are the histologic features of follicular carcinoma?
Split into two subtypes; minimally and widely invasive. Capsular and vascular invasion are the defining features.
What are the cytologic features of follicular carcinoma?
Marked cellularity, predominance of microfollicles and/or trabeculae, scant colloid.
How do hurthle cell tumors cytologically differ from follicular neoplasms?
Look for more atypia, large nucleolus. Noncohesive with pseudopsammoma bodies.
Recite the variants of papillary thyroid carcinoma.
Follicular, macrofollicular, oncocytic, Warthin-like, clear cell, diffuse sclerosing, columnar, tall-cell, solid, cribriform-morular, and fasciitis-like stroma.
What are the underlying genetic features of PTC?
RET/PTC translocation, TRK rearrangements, RAS and BRAF point mutations. PAX/PPARy?
Describe the cytology of PTC.
Sheets, papillae, or microfollicles of cells with grooves and pseudoinclusions. May have multinucleated giant cells and variable colloid.
What are poorly differentiated carcinomas? What are their 3 histologic patterns? What are the defining features?
Malignant thyroidal carcinomas that fall in between the differentiated carcinomas and the anaplastic.
Insular, trabecular, and solid.
Ki67 is 10-30%, with 3+ mitoses per 10hpf
Describe the cytology of anaplastic thyroid carcinoma
Obvious, whopping malignancy with extreme atypia, tumor diathesis…can’t mistake this.
What is the significance of squamous cell carcinoma of the thyroid?
It affects the same patients as and behaves the same way as anaplastic thyroid carcinoma.
What is the cell of origin of MTC? Who does it affect?
Parafollicular C cell
Most cases are actually sporadic (adult); only 10-20% are associated with MEN (peds cases)
What are the HISTOLOGIC features of MTC?
Sheets, nests, or ribbons of variably shaped neuroendocrine nuclei (no nucleoli) frequently with pseudoinclusions and amyloid.
What are the cytologic features of MTC?
Noncohesive cells with frequent pseudoinclusions and inconspicuous nucleoli. Look for amyloid and red cytoplasmic granules (calcitonin?)
Why should MTC always be considered in lymph node evaluations?
50% of cases already have lymph nodal spread at the time of diagnosis.
Who does thyroid lymphoma affect, and what are the patterns seen?
Patients with Hashimoto’s thyroiditis (confers 60x risk). Falls into EMZL, DLBCL, and mixed patterns.
What are the cytologic features of EMZL of thyroid?
Look for numerous small lymphoid cells including centrocytes, plasma cells, and monocytoid B cells.
What are the cytologic features of DLBCL of thyroid?
Look for large monotonous cells (centroblasts vs immunoblasts), maybe Burkitt’s-like cells.
What are the most common metastases to thyroid?
Lungs, esophagus, breast, kidney
What is the role of the AUS/FLUS category?
Describes entities that do not satisfy suspicious or malignant criteria. Try to keep to <7% of FNA diagnoses.
Try to recall 8 scenarios appropriate for the diagnosis of AUS/FLUS.
Microfollicles with sparse overall cellularity
Hurthle cells with sparse overall cellularity
Hurthle cells with history of thyroiditis
Atypia hindered by artifact
Random nuclear atypia
Atypical cyst lining cells
Marked anisonucleosis
Atypical lymphoid infiltrate
What are the cytologic features of parathyroid cells?
Cohesive sheets, ribbons, and acini of cells with coarsely granular chromatin and moderately granular cytoplasm. No colloid!
What roles do molecular probe tests play in thyroid FNA?
Most valuable for elucidating suspicious and atypical cases that cannot be outright called malignant or benign.
