ENT - Thyroid Neoplasms PDF

Thyroid Gland SURGICAL ANATOMY AND EMBRYOLOGY thyroid medial anlage derives from the ventral diverticulum of the endoderm from the first and second pharyngeal pouches at the foramen cecum 4 to 7 of gestation The diverticulum descends from the base of the tongue to its adult pretracheal pos...

Thyroid Gland SURGICAL ANATOMY AND EMBRYOLOGY thyroid medial anlage derives from the ventral diverticulum of the endoderm from the first and second pharyngeal pouches at the foramen cecum 4 to 7 of gestation The diverticulum descends from the base of the tongue to its adult pretracheal position through a midline anterior path with the primitive heart and great vessels  thyroid gland is composed of two lateral lobes connected by a central isthmus weighs 15 to 25 g in adults measures about 4 cm in height, 1.5 cm in width, and 2 cm in depth  superior pole lies posterior to the sternothyroid muscle and lateral to the inferior constrictor muscle and the posterior thyroid lamina inferior pole can extend to the level of the sixth tracheal ring  The thyroid is enclosed between layers of the deep cervical fascia in the anterior neck Posteriorly, the middle layer of the deep cervical fascia condenses to form the posterior suspensory ligament, or Berry ligament, that connects the lobes of the thyroid to the cricoid cartilage and the first two tracheal rings Blood supply to and from the thyroid gland involves two pairs of arteries three pairs of veins dense system of connecting vessels within the thyroid capsule inferior thyroid artery arises as a branch of the thyrocervical trunk lies anterior to the recurrent laryngeal nerve (RLN) in approximately 70% of patients inferior thyroid artery is also the primary blood supply for the parathyroid glands superior thyroid artery branch of the external carotid artery and courses along the inferior constrictor muscle with the superior thyroid vein to supply the superior pole of the thyroid  RLN provides motor supply to the larynx and some sensory function to the upper trachea and subglottic area right RLN leaves the vagus nerve at the base of the neck loops around the right subclavian artery returns deep to the innominate artery back into the thyroid bed approximately 2 cm lateral to the trachea The nerve enters the larynx between the arch of the cricoid cartilage and the inferior cornu of the thyroid cartilage left RLN leaves the vagus at the level of the aortic arch loops around the arch lateral to the obliterated ductus arteriosus The nerve returns to the neck posterior to the carotid sheath and travels near the tracheoesophageal groove along a more medial course than the right RLN parathyroid glands caramel-colored glands that weigh 30 to 70 mg Superior parathyroid glands are derived from the fourth pharyngeal pouch inferior parathyroid glands originate from the third pharyngeal pouch subtle distinction of tan and yellow coloration permits differentiation from adjacent fatty tissue with trauma, the glands can become mahogany in color  Four parathyroid glands exist in 80% of patients at least 10% of patients have more than four glands glands are situated on the undersurface of the thyroid gland in predictable locations superior glands are located at the level of the cricoid cartilage, usually medial to the intersection of the RLN and the inferior thyroid artery inferior glands are more variable in location. These glands may be on the lateral or posterior surface of the lower pole  Thyroid neoplasms represent almost 95% of all endocrine tumors 2.5% of all malignancies incidence of thyroid nodules is significantly greater and affects approximately 4% to 7% subset of thyroid cancers is particularly aggressive and has the potential for devastating morbidity High-definition ultrasound and fine-needle aspiration biopsy- hallmark of diagnostic evaluation for thyroid neoplasia Surgery remains the mainstay of treatment  prognosis for young patients with differentiated thyroid cancer is typically excellent RISK FACTORS AND ETIOLOGY Women are three times more likely than men to develop differentiated thyroid cancer Median age at diagnosis is 51 years (women- 50 to 54 years and men- 65 to 69 years) Exposure to ionizing radiation increases patient risk for the development of thyroid carcinoma familial and genetic contributions need to be fully evaluated History and Physical Examination Patients younger than 20 years- 20% to 50% incidence of malignancy when presenting with a solitary thyroid nodule. Nodular disease is more common in older patients(men older than 40 years and women older than 50 year) children may present with more advanced disease and even cervical metastases malignancy in older patients has a considerably worse prognosis Men often have more aggressive malignancies than women overall incidence of thyroid nodules and malignancy is higher in women History and Physical Examination rapid growth of a preexisting or new thyroid nodule is concerning Throat or neck pain frequently occurs with hemorrhage into a benign nodule Patients should be carefully questioned regarding any compressive or invasive symptoms, such as voice change, hoarseness, dysphagia, or dyspnea physical examination of a patient with a thyroid nodule begins with careful palpation should determine whether the lesion is solitary or the dominant nodule in a multinodular gland  Asking the patient to swallow may assist in the examination Palpable nodules are typically 1 cm or larger firmness of the nodule may be associated with an increased risk of carcinoma by twofold to threefold Palpable cervical nodes adjacent to the thyroid nodule increase the suspicion for malignancy mobility of the nodule relative to the laryngotracheal complex and adjacent neck structures should be evaluated All patients with a thyroid lesion should have a complete vocal cord examination FNAC has become the procedure of choice in the evaluation of thyroid nodules findings are highly sensitive and specific Successful FNAC categorizes nodules as benign, malignant, or suspicious Ultrasonography (US) is tremendously useful and sensitive. These studies detect nonpalpable nodules and differentiate between cystic and solid nodules provide key baseline information regarding nodule size and architecture  Radionuclide scanning- assesses the functional activity of a thyroid nodule and the thyroid gland less radioactivity than the surrounding thyroid tissue- cold/nonfunctioning Thyroid Cyst Approximately 15% to 25% of all thyroid nodules are cystic or have a cystic component presence of a cyst does not signify a benign lesion can result from congenital, developmental, or neoplastic causes thyroid cyst should be drained completely If a cyst persists after three drainage attempts, uspicion for carcinoma should increase. Papillary Carcinoma most common form of thyroid malignancy accounts for about 80% of all thyroid cancer occurs in patients 30 to 40 years old more common in women (female/male ratio of 2 : 1) Predominant thyroid malignancy in children (75%) Most patients with papillary carcinoma present with a slow growing, painless mass in the neck and are often euthyroid primary lesion is confined to the thyroid gland 30% clinically evident cervical nodal disease  gross examination: papillary carcinoma is firm, white, and not encapsulated Histologically: arise from thyroid follicular cells and contain papillary structures that consist of a neoplastic epithelium overlying a true fibrovascular stalk Prominent nucleoli account for the “Orphan Annie eye” appearance management Most patients with papillary carcinoma do well regardless of treatment When patients present with biopsy-proven disease or indications of disease in both lobes, total thyroidectomy is generally the procedure of choice Follicular Carcinoma represent approximately 10% of thyroid malignancies. The mean age of presentation is 50 years Women more commonly have this lesion, (female/male ratio of 3 : 1) occur more frequently in iodine deficient areas Patients usually present with a solitary thyroid nodule, although some patients may have a history of longstanding goiter and recent rapid increase in nodule size lesions are typically painless, but hemorrhage into the nodule may cause pain  Cervical lymphadenopathy is uncommon at initial presentation distant metastases are more frequently encountered Definitive preoperative diagnosis is usually impossible by FNAC Differentiation between follicular adenoma and follicular carcinoma requires an evaluation of the thyroid capsule for invasion or identification of vascular invasion  tends to manifest as solitary, encapsulated lesions Histologic findings are necessary to distinguish benign and malignant lesions Malignant lesions are differentiated by the identification of capsular invasion and potential microvascular invasion of vessels along the tumor capsule The degree of capsular invasion is important for patient prognosis.  Patients diagnosed with a follicular lesion by FNAC may have a thyroid lobectomy with isthmectomy performed short-term observation with follow-up ultrasound Total thyroidectomy may be preferred in older patients with a nodule greater than 4 cm in size diagnosed by FNAC as follicular neoplasm Hürthle Cell Tumor a subtype of follicular cell neoplasm can be found in patients with Hashimoto thyroiditis or Graves disease or within a nodular goiter These tumors are derived from oxyphilic cells of the thyroid gland typically diagnosed by FNAC, and approximately 20% of these lesions are malignant Hürthle cell carcinomas represent approximately 3% of all thyroid malignancies  tend to behave more aggressively than papillary and follicular carcinomas more likely to metastasize to cervical nodes and distant sites  FNAC of Hürthle cell tumors typically show hypercellularity and the presence of eosinophilic cells  The clinical approach to Hürthle cell tumors is similar to that for follicular neoplasms Hürthle cell adenoma-resection of the affected lobe and isthmus is sufficient Invasive findings for Hürthle neoplasms on formal pathology generally warrant a total or completion thyroidectomy they are less amenable to radioiodine therapy because of their decreased tendency to take up radiolabeled iodine Postoperative management should include TSH suppression and thyroglobulin monitoring and periodic US evaluation of the central and lateral cervical compartments Medullary Thyroid Carcinoma distinct category of disease and represent approximately 3% of all thyroid carcinomas malignancies arise from parafollicular C cells and may secrete calcitonin, CEA, histaminidases, prostaglandins, and serotonin Measurement of secreted calcitonin is useful for the diagnosis of MTC and for postsurgical surveillance for residual and recurrent disease  Women and men are equally affected by MTCs Patients usually present with a neck mass associated with palpable cervical lymphadenopathy (≤20%) Local pain is more common in these patients and indicates the presence of local invasion spontaneous unifocal lesions in patients 50 to 60 years old without an associated endocrinopathy Two forms of MEN syndrome are associated with MTC Pathology MTC originates from parafollicular C cells of neuroectodermal origin cells descend to join the thyroid gland proper and are concentrated mainly in the lateral portions of the superior poles Most MTC lesions are located in the middle and upper thyroid poles Grossly, the tumor is solid and firm and has a gray cut surface. The lesion is nonencapsulated but well circumscribed  Preoperative workup includes measurement of calcitonin and serum CEA CTscan of the chest and mediastinum and ultrasound examination of the neck are recommended Total thyroidectomy is the treatment of choice Because of the frequent involvement of cervical nodes, initial surgical management should include bilateral central compartment neck dissection When palpable lateral cervical nodes are present, treatment that includes an ipsilateral or bilateral comprehensive neck dissection (levels II through V) should be considered Anaplastic Carcinoma one of the most aggressive malignancies few patients have historically survived 6 months beyond initial presentation represent approximately 1% of all thyroid carcinomas typically occur in older patients Women are more commonly (3 : 2) 80% of these malignancies may occur with a coexisting carcinoma and may represent transformation of a well-differentiated thyroid cancer  Patients typically present with a rapidly enlarging neck mass, accompanied by pain, dysphonia, dysphagia, and dyspnea mass is quite large and is fixed to the tracheolaryngeal framework >60% have lateral neck lymph node at initial presentation  Grossly: shows areas of necrosis and macroscopic invasion of surrounding tissues, often with lymph node involvement Microscopically: sheets of cells with marked heterogeneity are present. Spindle, polygonal, and giant multinucleated cells are present with occasional foci of differentiated cells. management Management of anaplastic carcinoma is extremely difficult and requires a multidisciplinary approach Surgical resection may be considered if locoregional disease can be resected grossly complications Bleeding Complications Superior Laryngeal Nerve Injury Recurrent Laryngeal Nerve Injury Hypocalcemia Thank you