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follicular thyroid adenoma

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: 1) variety of patterns may be seen a) fetal, embryonal, simple, trabecular, spindle cell & colloidal b) various patterns of follicular adenomas tend to recapitulate embryologic development of the thyroid 2) mixed patterns are common 3) rarely progress to malignant tumors 4) follicular neoplasms average 3 cm in diameter, but may be up to 10 cm 5) infrequently, 2 or more follicular adenomas may be present 6) in larger adenomas, central necrosis may transform the adenoma into a cyst 7) occasionally foci of hemorrhage, fibrosis or calcification may be noted Genetics: - associated with defects in MINPP1 Laboratory: - serum TSH Special laboratory: - fine needle aspiration of thyroid nodule a) 15-30% chance of follicular thyroid carcinoma b) follicular thyroid carcinoma cannot be distinguished from follicular thyroid adenoma on FNA c) thyroid lobectomy or total thyroidectomy indicated for diagnosis Radiology: -> radioactive iodine uptake (RAIU) test (hot nodules are almost always benign) Differential diagnosis: - follicular thyroid carcinoma Management: 1) thyroid lobectomy or total thyroidectomy generally indicated for diagnosis 2) treat hyperthyroidism resulting from hyperfunctioning nodule a) radiactive iodine ablation b) thyroidectomy c) avoid iodine (may precipitate thyrotoxicosis) 3) no treatment necessary for euthyroid patients a) provided diagnosis of follicular thyroid adenoma vs follicular thyroid carcinoma confirmed* b) follow-up every 6 months to monitor for development of hyperthyroidism 4) levothyroxine a) may reduce size of non-functional benign cysts b) use in benign non-functional nodules is controversial [2] c) 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]

Related

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)

Specific

colloid thyroid adenoma fetal thyroid adenoma spindle cell thyroid adenoma trabecular thyroid adenoma

General

adenoma thyroid neoplasm (nodule)

References

  1. Cotran et al Robbins Pathologic Basis of Disease, 5th ed. W.B. Saunders Co, Philadelphia, PA 1994 pg 1134
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2012, 2015, 2018.
  3. 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 PMID: 27078145 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 PMID: 27077657 http://oncology.jamanetwork.com/article.aspx?articleid=2513246