follicular thyroid adenoma
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Etiology
- somatic mutations in the TSH receptor gene account for evolution of toxic follicular adenomas
Epidemiology
- vast majority of thyroid adenomas are follicular adenomas
Pathology
- variety of patterns may be seen
- fetal, embryonal, simple, trabecular, spindle cell & colloidal
- various patterns of follicular adenomas tend to recapitulate embryologic development of the thyroid
- mixed patterns are common
- rarely progress to malignant tumors
- follicular neoplasms average 3 cm in diameter, but may be up to 10 cm
- infrequently, 2 or more follicular adenomas may be present
- in larger adenomas, central necrosis may transform the adenoma into a cyst
- occasionally foci of hemorrhage, fibrosis or calcification may be noted
Genetics
- associated with defects in MINPP1
Laboratory
Diagnostic procedures
- fine needle aspiration of thyroid nodule
- 15-30% chance of follicular thyroid carcinoma
- follicular thyroid carcinoma cannot be distinguished from follicular thyroid adenoma on FNA
- thyroid lobectomy or total thyroidectomy indicated for diagnosis
Radiology
- radioactive iodine uptake (RAIU) test (hot nodules are almost always benign)
Differential diagnosis
Management
- thyroid lobectomy or total thyroidectomy generally indicated for diagnosis
- treat hyperthyroidism resulting from hyperfunctioning nodule
- radiactive iodine ablation
- thyroidectomy
- avoid iodine (may precipitate thyrotoxicosis)
- no treatment necessary for euthyroid patients
- provided diagnosis of follicular thyroid adenoma vs follicular thyroid carcinoma confirmed*
- follow-up every 6 months to monitor for development of hyperthyroidism
- levothyroxine
- may reduce size of non-functional benign cysts
- use in benign non-functional nodules is controversial[2]
- contraindicated with autonomous hyperfunctioning nodules
* Much ado about removing the name 'cancer' from noninvasive encapsulated follicular variant of papillary thyroid carcinoma which seems to amount to follicular thyroid adenoma versus follicular thyroid carcinoma[3]
More general terms
More specific terms
- colloid thyroid adenoma
- fetal thyroid adenoma
- spindle cell thyroid adenoma
- trabecular thyroid adenoma
Additional terms
- follicular thyroid carcinoma
- levothyroxine (Synthroid, Levoxyl, Levothroid, Unithroid, Levolet, Novothyrox, Thyrotab)
- radioactive iodine uptake (RAIU) test
- thyroid-stimulating hormone (TSH) in serum; thyrotropin in serum
- thyrotropin receptor; thyroid-stimulating hormone receptor; TSH-R (TSHR LGR3)
References
- ↑ Cotran et al Robbins Pathologic Basis of Disease, 5th ed. W.B. Saunders Co, Philadelphia, PA 1994 pg 1134
- ↑ 2.0 2.1 Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2012, 2015, 2018.
- ↑ 3.0 3.1 Nikiforov YE, Seethala RR, Tallini G et al Nomenclature Revision for Encapsulated Follicular Variant of Papillary Thyroid Carcinoma. A Paradigm Shift to Reduce Overtreatment of Indolent Tumors. JAMA Oncol. Published online April 14, 2016 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/27078145 <Internet> http://oncology.jamanetwork.com/article.aspx?articleid=2513250
Patel KN Noninvasive Encapsulated Follicular Variant of Papillary Thyroid "Cancer" (or Not)Time for a Name Change. JAMA Oncol. Published online April 14, 2016 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/27077657 <Internet> http://oncology.jamanetwork.com/article.aspx?articleid=2513246