thyroid nodules Flashcards
How are thyroid nodules usually discovered
Most are noted by patient, then noted by third party or detected by other tests. Ultrasound > CT > PET
How common are thyroid nodules and how often are they cancerous
Nearly 60% of people will get a thyroid nodule but only 10-15% are cancer.
List the most common benign and malignant thyroid masses
Benign: adenoma. Malignant: papillary (85-90%), follicular (5%), anaplastic (<2%), medullary (5%), lymphoma, sarcoma and metastatic are rare
Types of follicular/hurthle cell carcinomas
- minimally invasive- vascular or capsular invasion. 2. Widely invasive - more extensive
Papillary carcinoma characteristics
well differentiated, lymphatic spread, excellent prognosis
Papillary carcinoma histology
Papillae with vascular core, optically clear nuclei, neuclear pseudoinclusions, nuclear grooves, rare or absent mitoses, psammoma bodies
Anaplastic carcinoma characteristics
older age group, poor survival, rapidly growing mass
Patterns of anaplastic carcinoma
spindle cell, giant cells, squamoid cells
Medullary carcinoma histology
Solid proliferation of cells with granular cytoplasm (C cells), Highly vascular stroma, Hyalinized collagen and/or amyloid, May have Psammoma bodies
Immunostains for medullary carcinoma
Thyroglobulin negative, calcitonin positive, chromogranin positive
Thyroid lymphomas
large fleshy masses and background of autoimmune thyroiditis
List cancers which may metastasize to thyroid
melanoma, lung, head and neck, renal, breast, colon
Workup for thyroid nodules
- TSH. 2. If TSH is low, nuclear imaging. If TSH is high/normal ultrasound. 3. If ultrasound shows nodule, fine needle aspiration. If no nodule on US, don’t do FNA. 4. If FNA is benign, follow. If FNA is malignant, surgery. If FNA is inadequate, re-biopsy. If FNA is suspicious, scan.
Papillary carcinoma of thyroid histology
Highly cellular, +/- colloid, nuclear enlargement and elongation, nuclear grooves and pseudoinclusions, multiple small to large nucleoli, psammoma bodies, papillary cellular aggregates
define proto oncogene
Normal gene which codes for a protein that promotes normal cell division
Define oncogene
Mutated gene which codes for a protein that causes unregulated cell division. Oncogene activation causes tumors
Define tumor suppressor gene
Normal gene which codes for a protein that restrains cell division or that promotes cell differentiation, DNA repair or apoptosis. Tumor suppressor gene loss results in tumors
Molecular mechanisms of papillary carcinoma
RE/PTC rearrangement (20%), Ras point mutation (20%), and/or BRAF point mutation (40%) leads to cell growth and division
Molecuar mechanisms of follicular thyroid carcinoma
Pax8-PPARgamma gene rearangement/fusion leads to abnormal expression in thyroid cells and follicular thyroid carcinoma in 50%.
Describe the progression of thyroid tumor development.
thyroid follicular cell > follicular adenoma (Ras methylation) > follicular carcinoma (Pax8-PPARgamma fusion) > anaplastic carcinoma (p53 and Beta catenin mutations). Also thyroid follicular cell > papillary thyroid carcinoma (RET/PTC, Trk, Met, Ras, BRAF mutations). Also thyroid follicular cell > hyperfunctioning adenoma (TSH-R, g protein mutations)