| How is the embryology of the thyroid? | Evagination of the pharyngeal embryonic epithelium migrating from thyroglossal duct at base of the tongue to its final position
Anomalies that may occur are heter-ectopia (lingual thyroid, retrosternal thyroid and intratracheal thyroid)
Another anomaly which is the most common one the thyroid cyst (Cyst at the cervical midline level in front of the trachea, 2-3 cm mucinous/clear liquid, lined by epithelia (squamous) and thyroid tissue) |
| What are the pathologies of the thyroid? | Infectious, Hashimoto's thyroiditis, Subacute and granulomatous Thyroiditis (De Quevrain Thyroiditis), Lymphocytic subacute thyroiditis. |
| What is Hashimoto's Thyroiditis? | It is the most common cause of hypothyroidism in iodine adequate places, usually adults 45-65 yrs old 15: 1 (female to male), may affect children.
We see symmetrical enlargement of the gland (diffuse goiter w/nodular reinforcements) and intact capsule.
We see infiltration of parenchyma by mononuclear inflammatory infiltrate of small lymphocytes, plasma cells and well developed germinal center, follicles are atrophic lined in many areas by epithelial cells (Oxyphil cells/Hurthle cells high eosinophilic)
Fibrosis doesn't extend beyond the capsule and no venulitis (differs from Riedel's Thyroiditis) |
| What is De Quevarian Thyroiditis? | Less frequent than Hashimoto, 30-50 yrs old, 4:1 (F:M), uni or bilateral enlargement with no capsule involvement.
3 Phases (early [microabscess], Later [disruption of follicles, extravasation of colloid, infiltration of neutrophils and then replaced by lymphocytes, plasma cells and macrophages, which then provokes granulomatous reaction w/giant cells, healing may cause inflammation resolution/fibrosis]
Advanced stage [inflammatory infiltrates and fibrosis])
Different stages may coexist |
| What is Grave's Disease? | Diffuse toxic goiter, most common cause of hyperthyroidism, age 20-40 yrs 7:1 (F:M), Autoimmune disease with symmetrical increase in thyroid size, hypertrophy and hyperplasia.
Can reach weight of 80g, intact capsule.
Form small papillae that project to the follicular lumen (unlike papillary carcinoma papillae that have fibrovascular core)
Pale colloid w/scalloped margins, tall follicular cells, columnar and crowded, lymphoid infiltrate discrete and germinal centers are common. |
| What are diffuse and nodular goiters? | Goiter is most common thyroid pathology, thyroid dysfunction linked to iodine deficiency. Two types:
-Diffuse non toxic goiter (hyperplastic phase [gland diffuse and symmetrical increase in size (max 100-150g), follicules lined with tall epithelia form pseudopapilla, heterogenous appearance across the gland some giant some small], Colloid involution phase)
-Multinodular Goiter (cause of largest increase in size [2kg], compresses surrounding organs, multiple nodules sometimes gelatinous colloid, areas of hemorrhage/fibrosis/cystic transformation, inactive follicles/hyperplastic follicles. |
| What are neoplasia of thyroid? | Mostly Solitary palpable nodule, 4:1 (F:M), incidence increases with age, mostly benign in nature (10:1), thyroid cancers are mostly indolent (inactive), and usually solitray nodules are more neoplastic than multiple ones.
Red Flags (young pt, Men, Hx of irradiation
Multiple genetic pathways in thyroid carcinogenesis (PAX8/PPRAG unique for thyroid cancer/RET oncogene) |
| What are thyroid adenomas? | Usually follicular origin (follicular adenomas), often solitary, well limited and capsulated, compresses surrounding nonneoplastic thyroid tissues, well-defined intact capsule.
Average size 3 cm, color from red to gray-white, areas of remodeling may exist.
Microscopy (different architecture than surrounding thyroid tissue, regular cells/few mitoses, may get cutonuclear atypica but not sx of malignancy on their own, so when we see atypical signs (very rapid division, hypercells, atypia) we look at capsule if invaded/vascular invasion to differentiate it from carcinoma. |
| What are benign thyroid tumors other than adenoma? | Cysts (cystic transformation of follicles)
Lipoma, Hemangioma, Teratoma. |
| What are thyroid carcinomas? | Usually occur in adulthood [rare form of papillary occurs in children], Female predominance in young and middle aged, majority are well-differentiated [papillary and follicular] |
| What is papillary thyroid carcinoma? | 75-85%, 20-40, most often linked to exposure to ionizing radiation.
Macroscopy solitary or multifocal lesion, encapsulated/cyst/heterogenous, more often infiltrating stellar irregular outline, firm consistency whitish granular appearance.
Microscopy fibrovasclar stalk covered by cuboidal epithelium, mostly well-differentiated and orderly epithelium, but may be sometimes more anaplastic/pleonorphic. Papillary architecture (not always seen), ground glass nuclei, cytoplasmic invagination making intranuclear inclusion appearance which are sufficient in dx of papillary carcinoma.
Psammoma bodies present in lesion pathogneumonic for Papillary carcicinoma
Often lymph invasion occurs (50%) but uncommon vascular invasion alot of variants most common is encapsulated follicular variant |
| What is follicular thyroid carcinoma? | 10-15%, 40-50 yrs old.
Macroscopy well demarcated nodule or widely invasive mass, DD: Adenoma.
Microscopy: most composed of uniform cells forming small follicles, Hurthle cells may be seen, may be widely invasive infiltrating the thyroid parenchyma and extrathyroid soft tissues/minimally invasive, latter one is sharply demarcated may be impossible to distinguish from follicular adenoma, only seen by histology to see capsular invasion |
| What is medullary thyroid carcinoma? | 5%, neuroendocrine tumors from parafollicular cells/C cells of the thyroid, measurement of calcitonin imp in dx and postop, sporadic (70%), adult between 40-50 yrs, 30% familial in MEN2A/2B (usually young/children), or famlial w/out MEN
Solitary nodule/multiple lesions involving both lobes of thyroid, larger lesions contain areas of necrosis/hemorrhage and may extend through thyroid capsule.
Micrscopy (polygonal cells, form nests/trabeculae/follicles, amyloid deposits present in stroma in many cases and are distinctive features.
Calcitonin seen in cytoplasm of cells, and stromal amyloid
is one of the characteristics of medullary carcinoma of multicentric C cell hyperplasia in surrounding thyroid parenchyma (absent in sporadic form)
Foci of C cell hyperplasia represent precursor lesion (believed) |
| What is anaplastic thyroid carcinoma? | undifferentiated tumors of the thyroid follicular epithelium, accounting for less than 5% of thyroid tumors.
They are aggressive, with a mortality rate approaching 100%.
Patients with anaplastic carcinoma are older than those with other types of thyroid cancer, with a mean age of 65 years.
Approximately one-fourth of patients with anaplastic thyroid carcinomas have a history of a well-differentiated thyroid carcinoma, and another
one-fourth harbor a concurrent well-differentiated tumor in the resected specimen.
Anaplastic carcinomas manifest as bulky masses that typically grow rapidly beyond the thyroid capsule into adjacent neck structures.
On microscopic examination, these neoplasms are composed of highly anaplastic cells, which may be large and pleomorphic or spindle shaped and in some cases mixture of the two cell types.
Foci of papillary or follicular differentiation may be present in some tumors, suggesting origin from a better-differentiated carcinoma. |
