8.1 Introduction
The solitary thyroid nodule must be carefully evalu- ated because of the risk of malignancy, however, se- lective management is paramount due to the high frequency of benign lesions. While 4–7% of the adult population in the USA have a palpable thyroid nod- ule [1], the vast majority of these patients have benign disease, and do not require surgical resection.
This chapter focuses on the use of lobectomy for nodules suspicious but not diagnostic for carci- noma, as well as algorithms for treatment of diag- nosed thyroid carcinoma. The extent of surgery for malignant thyroid disease is also discussed, along with strategies for risk stratification for treatment of differentiated thyroid cancer. Follicular cell-derived thyroid cancers, including papillary thyroid cancer, follicular thyroid cancer, and Hürthle cell cancer are highlighted.
8.2 Lobectomy
for Suspicious Lesions
Evaluation of a palpable solitary nodule in the thyroid gland should begin with a comprehensive history and physical examination. It is typically impossible to dis- tinguish a benign nodule from a malignant nodule by palpation, however, there are some clinical findings that are indicative of malignant disease. A history of a hard and relatively fast growing nodule is associated with a higher risk for malignancy when compared with a soft and slowly growing nodule. Furthermore, the presence of a solitary nodule is more indicative of malignancy, whereas a multinodular thyroid is more consistent with benign disease. Thyroid function studies may also be useful, since a suppressed thy- roid-stimulating hormone (TSH) level is suggestive of benign pathology, as it is uncommon for malignant lesions to cause thyrotoxicosis or thyroiditis [2].
Further evaluation of the solitary nodule is best done by ultrasound and fine-needle aspiration (FNA).
The ultrasound examination of the thyroid gland al- lows accurate evaluation of the thyroid nodule itself as well as the surrounding thyroid tissue (Fig. 8.1).
Characterization of the nodule includes the size, shape, solid versus cystic nature, the presence of calci- fications in the nodule, and the nature of the borders (smooth, irregular, etc.). The use of ultrasound-guided FNA can improve the diagnostic accuracy (Fig. 8.2), but interpretation of the aspirate for definitive diag- nosis may still not be possible. In cases of follicular neoplasia, FNA is limited in its ability to distinguish malignant from benign disease, since the diagnosis of follicular carcinoma is histological. Specifically, iden- tification of capsular or vascular invasion is necessary for diagnosis of malignant disease. This scenario is similar when dealing with Hürthle cell neoplasms.
Although cytological findings of FNA are sufficient for diagnosis in approximately 85% of specimens, 15% of aspirates fail to yield satisfactory results [3,4].
In such cases, pathology reports may be suspicious for malignant disease, and approximately 20% of such suspicious lesions will actually be malignant Hürthle
8 Surgery for the Solitary Thyroid Nodule
Prabhat K. Bhama and Gerard M. Doherty
Contents
8.1 Introduction . . . 91
8.2 Lobectomy for Suspicious Lesions . . . 91 8.3 Treatment for Differentiated
Thyroid Cancers . . . 93 8.3.1 Principles . . . 93
8.3.2 Treatment: Papillary Thyroid Cancer . . . 93 8.3.2.1 Total Thyroidectomy . . . 93
8.3.2.2 Unilateral Lobectomy and Isthmusectomy . . . 95
8.3.2.3 Recommendations for Extent of Surgery . . . 96 8.3.2.4 Lymph Node Dissection . . . 96
8.3.3 Treatment: Follicular Thyroid Cancer . . . 98 8.3.4 Treatment: Oncocytic (Hürthle
Cell) Thyroid Cancer . . . 98
8.4 Risk Stratification for Cancer Treatment . . . 98 8.5 Summary . . . 98
References . . . 99
Fig. 8.1 Longitudinal view of the left thyroid lobe, with a complex cystic and solid lesion in the mid to lower portion of the lobe. There is a second smaller cystic lesion in the upper pole of the gland. The cystic nature of these lesions is empha- sized by the posterior acoustic enhancement visible as the whiter areas posterior (lower on the figure) to the thyroid lobe
Fig. 8.2 Ultrasound-guided fine-needle aspiration (FNA) of a palpable left thyroid lobe lesion.
The ultrasound technique is used to direct the needle (arrows) to the le- sion that is to be sampled. Although ultrasound is not strictly necessary for the sampling of palpable lesions, it is helpful for directing the needle to a specific area within the target lesion. For non-palpable lesions, ultrasound in necessary for FNA cytology
or follicular neoplasms. While some have suggested the employment of 123I scintigraphy in cases of suspi- cious nodules, this test is not sufficient for uncovering malignant disease. The presence of “hot” nodules on 123I scintigraphy is suggestive of benign disease, since malignant neoplasms typically manifest as “cold”
nodules. However, patients with “hot” nodules on 123I scan have occasionally been found to have thyroid cancer upon further investigation [5].
Thus, there are currently no investigative proce- dures available to definitively distinguish benign from malignant disease in patients with suspicious lesions of indeterminate cytology. A recent study indicated that experienced pathologists may be accurate when predicting benign disease using FNA, however, the authors determined that the predictive value of the test was not enough to preclude surgical resection [6]. As such, suspicious lesions are considered to be positive for cancer, and should be treated with sur- gical resection to avoid the adverse consequences as- sociated with untreated thyroid cancer. The principal surgical approach to solitary, undetermined nodule is ipsilateral lobectomy. The reason for primary removal of the entire ipsilateral thyroid lobe is to avoid seri- ous complications, since if further surgery is needed a reoperation is difficult and may be harmful in scarred tissue.
8.3 Treatment for Differentiated Thyroid Cancers
8.3.1 Principles
Differentiated carcinoma of the thyroid includes both papillary and follicular variants. The primary treatment for these cancers is resection. Although surgical intervention is clearly indicated, contro- versy remains regarding the extent of thyroid tissue that should be removed during the initial operation.
Whereas total thyroidectomy may help ensure removal of all neoplastic tissue, it leaves the patient with no thyroid tissue, necessitating lifelong thyroid hormone supplementation and exposing the patient to the risk of bilateral dissection of the adjacent normal neck structures. Alternatively, more conser- vative procedures may leave inconspicuous residual cancer within the patient. Unfortunately, there are no prospective randomized clinical trials evaluating the extent of thyroidectomy, adjuvant radioactive iodide therapy, and TSH suppressive therapy. Because of the relatively good prognosis and low incidence of papillary thyroid cancer (PTC), such a study would
require a large multicenter trial with long follow- up time. It is unlikely that such trials will ever be performed.
Three primary surgical strategies exist for the treatment of differentiated thyroid cancer: total thy- roidectomy, near-total thyroidectomy, and lobectomy with isthmusectomy. Total thyroidectomy involves removal of the entire thyroid gland and its capsule, whereas near-total thyroidectomy preserves the pos- terior capsule of the thyroid contralateral to the neo- plasm. These two procedures are generally considered together as completely ablative approaches to thyroid carcinoma. Unilateral lobectomy and isthmusectomy is removal of the lobe ipsilateral to the lesion, and re- moval of the thyroid isthmus. This approach allows preservation of normal thyroid tissue, thereby obvi- ating the need for lifelong thyroid hormone supple- mentation. In addition, unilateral lobectomy with isthmusectomy essentially eliminates the risk for hy- poparathyroidism and bilateral vocal cord paralysis.
Subtotal thyroidectomy is a procedure in which pres- ervation of several grams of thyroid tissue is involved.
Due to higher complication rates encountered when subsequent surgery is indicated, subtotal thyroidec- tomy is not a recommended treatment option for pa- tients with differentiated thyroid cancer [7].
Regardless of the surgical approach chosen, the function of the vocal cords should be assessed prior to surgery by noting any history of voice changes.
Examination of the larynx by indirect laryngoscopy as a visual survey for vocal cord mobility is indicated whenever there is a history or examination finding of vocal changes. In the case of unilateral vocal cord pa- ralysis, extreme caution should be taken to preserve the contralateral recurrent laryngeal nerve to avoid acute airway compromise. The surgical team should also be prepared to create an alternative airway (i.e., tracheostomy) if the need arises during surgery or postoperatively.
8.3.2 Treatment: Papillary Thyroid Cancer 8.3.2.1 Total Thyroidectomy
Total thyroidectomy is a safe and effective primary
treatment for patients with PTC. In patients with
high-risk lesions or extrathyroidal tumor extension,
it is generally accepted that total thyroidectomy is
the appropriate treatment. However, in patients with
low-risk lesions, the extent of surgical resection is
controversial. Two key justifications exist for the use
of near-total or total thyroidectomy in patients with
PTC. First, removal of the entire thyroid gland may include the excision of cancer that was occult on the preoperative assessment, and second, the postop- erative follow-up surveillance for recurrent disease is more sensitive if the entire thyroid is removed. Af- ter a total or near-total thyroidectomy, postoperative radioactive iodine can be used to identify and ablate any residual thyroid cancer, and serum thyroglobulin is a more accurate marker of recurrent or persistent PTC following total thyroidectomy when compared with more conservative resections of thyroid tissue.
Advocates of more conservative procedures con- tend that there is a higher risk of complications fol- lowing total thyroidectomy. Nonetheless, complica- tion rates less than 2% after total thyroidectomy have been reported by numerous surgeons with experience in total thyroidectomy (Table 8.1). Factors determin- ing the risk for complication from total thyroidectomy include: the extent of thyroid disease, the experience of the surgeon, and the anatomic variation of the para- thyroid glands, recurrent laryngeal nerves, and exter- nal laryngeal nerves [8–10]. Major complications of total thyroidectomy include vocal cord paralysis sec- ondary to recurrent laryngeal nerve injury, and hypo- calcemia due to injury or resection of the parathyroid glands. Regardless, many surgeons achieve compara- ble complication rates for total thyroidectomy, near- total thyroidectomy, and more conservative proce- dures [11,12]. Amongst the <2% of patients who had complications after total thyroidectomy, tumors were more likely to be more invasive and involve the recur- rent laryngeal nerve, thereby necessitating resection of the nerve. While these data indicate that compli- cations following total thyroidectomy are rare, they are reported from surgeons with extensive operative experience doing total thyroidectomy. In the hands of less experienced surgeons, complication rates may be higher. Therefore, for patients with PTC necessitating
total or completion thyroidectomy, surgical treatment is best implemented by the experienced surgeon.
Papillary thyroid cancer often exists with intra- glandular multifocal disease that may not be identi- fied upon initial evaluation. In a study of 105 patients, Katoh et al. found that intraglandular cancer foci (other than the tumor regarded as the primary focus) were present in over 78% of patients. Moreover, these multicentric lesions were found in the contralateral lobe in 61%. The authors concluded that intraglandu- lar metastasis is an important characteristic of PTC [13]. This has also been demonstrated in a high pro- portion of microcarcinomas of the thyroid, which harbor bilateral foci of disease [14].
A more recent study indicated that approximately 44% of 182 patients studied harbored histologically confirmed PTC at completion thyroidectomy. This bilaterality was independent of risk classification.
Bilateral tumors at completion thyroidectomy were present in patients of both high- and low-risk classi- fications. This study suggests total thyroidectomy in order to eradicate all neoplastic tissue in patients with PTC. In addition, the authors recommended comple- tion thyroidectomy for patients with a history of PTC that were initially treated with more conservative sur- gical therapy [15].
Hay et al., from the Mayo clinic, studied local re- currence, nodal and distant metastases in patients with low-risk PTC based on the AMES prognostic classification system. They found that patients who underwent lobectomy for PTC had a higher recur- rence rate (14%) and nodal metastases (19%) than those patients treated with procedures involving both lobes. However, they found no significant difference in survival rate and distant metastases [16]. Other studies have demonstrated that between 5% and 10%
of recurrences of thyroid cancer occur in the contra- lateral lobe [17], indicating that total thyroidectomy
Table 8.1 Complications reported after total thyroidectomy Authors, year Number
of patients
Transient nerve paresis;
number (%)
Permanent nerve paresis;
number (%)
Transient
hypoparathyroidism;
number (%)
Permanent
hypoparathyroidism;
number (%) Thompson, 1978
[44]
165 NR 0 NR <2%
Clark, 1988 [45] 160 4 (2.5%) 3 (2%) NR 1 (0.6%)
Ley, 1992 [12] 124 1 (0.8%) 1 (0.8%) 13 (10%) 2 (1.6%)
Tartaglia, 2003 [46]
1,636 31 (1.9%) 15 (0.9%) NR 14 (0.9%)
Rosato, 2004 [26] 9,599 195 (2%) 94 (1%) 797 (8.3%) 163 (1.7%)
during the initial operation may have been benefi- cial in these patients. Moreover, complications due to central neck recurrence are the cause of death in 50% of patients who die from recurrent thyroid car- cinoma [18]. In addition, a review of 1,599 patients with differentiated thyroid carcinoma concluded that patients with well-differentiated thyroid cancers who die from their disease most likely die secondary to lo- cal recurrence [19]. Such complications may best be avoided by implementation of total thyroidectomy and lymphadenectomy as the primary surgical treat- ment for differentiated thyroid cancers.
Finally, there is approximately a 1% risk of progres- sion from a differentiated thyroid cancer to anaplastic thyroid cancer. Whereas the prognosis of PTC is very good, anaplastic thyroid cancer results in near uni- form lethality. Therefore, elimination of all PTC via total thyroidectomy may prevent progression to ana- plastic thyroid cancer from residual tissue left behind during thyroid lobectomy and isthmusectomy.
Total thyroidectomy and central neck lymph node dissection is indicated for virtually all patients with PTC when postoperative radioactive iodine is consid- ered (see below for discussion of lymph node man- agement). In patients with excellent prognosis (tumor size less than 1 cm, confined to the thyroid without evidence of any metastatic disease, in an otherwise healthy female less than 45 years of age), more con- servative approaches may be used. However, lower re- currence and mortality rates are associated even with patients who have low-risk PTC and undergo total thyroidectomy [16,20]. Moreover, patients undergo- ing total thyroidectomy can also benefit from more accurate assessment of disease recurrence or residual disease using serum thyroglobulin levels. In addition, postoperative radioactive iodine scanning and abla- tion are more effective in patients after total thyroid- ectomy. In cases where injury to the recurrent laryn- geal nerve or parathyroid glands cannot be avoided, near-total thyroidectomy can be employed to leave behind a small amount of thyroid tissue, followed by ablation of residual tissue with radioactive iodine.
8.3.2.2 Unilateral Lobectomy and Isthmusectomy
The use of unilateral lobectomy and isthmusectomy for the treatment of differentiated thyroid cancers is supported by two arguments. First, unilateral proce- dures can avoid the risk of some potential complica- tions of bilateral procedures. Second, some studies have failed to demonstrate a survival benefit of total
thyroidectomy compared to lobectomy and isthmu- sectomy.
Because of the proximity of the recurrent laryn- geal nerve with respect to the fascia surrounding the thyroid (the visceral portion of the pretracheal layer of deep cervical fascia), it seems plausible to assume that bilateral procedures place the recurrent laryn- geal nerve at greater risk for injury than unilateral procedures. On the one hand, unilateral injury to the recurrent laryngeal nerve leaves the ipsilateral vocal cord paralyzed in the paramedian position, result- ing in hoarseness of the voice. In addition, the voice may often appear breathy, secondary to incomplete adduction of the vocal cords. This complication can be treated with medialization of the paralyzed cord via type I thyroplasty. However, morbidity is substan- tially increased, along with healthcare costs. On the other hand, bilateral recurrent laryngeal nerve injury can result in acute airway obstruction. This may pres- ent as postoperative stridor and dyspnea, and may re- quire endotracheal reintubation with establishment of an alternative airway via tracheostomy. The incidence of recurrent laryngeal nerve injury during total thy- roidectomy is approximately 1–1.5% and likely much less in the hands of the experienced surgeon.
Total thyroidectomy also places the patient at risk for lifelong hypocalcemia if all parathyroid tissue is unintentionally resected with the thyroid gland, while unilateral procedures do not. In fact, the most common underreported morbidity that does occur following thyroidectomy is likely transient hypocal- cemia [21] that can be monitored effectively without difficulty by frequent postoperative examinations of the patient. However, a recent study of over 450 patients who underwent total thyroidectomy demon- strated that permanent hypocalcemia occurred in only 0.7% of all patients. The authors noted that high serum phosphorus level on postoperative day 7 was the only independent factor predicting permanent hypoparathyroidism, and thus, permanent hypocal- cemia [22].
One retrospective study of 109 patients with non-
medullary thyroid cancer with 5- to 30-year follow-
up demonstrated that significantly more complica-
tions occur with total thyroidectomy when compared
with partial thyroidectomy. Furthermore, no differ-
ences in cancer mortality or recurrence rates amongst
patients treated with total thyroidectomy versus par-
tial thyroidectomy were found. The authors therefore
recommended the use of partial thyroidectomy for
non-medullary thyroid cancers [23]. A more recent
study demonstrated that there is no survival benefit
with total thyroidectomy when compared with partial
thyroidectomy in patients with PTC in both low- and high-risk prognostic groups [24].
A recent study of incidental multifocal papillary thyroid microcarcinomas (less than or equal to 1 cm) found that subtotal thyroidectomy followed by adju- vant radioiodine therapy is a therapeutic option for patients with incidental multifocal microcarcinomas.
However, the authors did note that future studies should be pursued for further evaluation of this tech- nique [25].
Despite the significant, life-changing complica- tions reported in the literature secondary to total thy- roidectomy, major complications occur in less than 2% of all thyroid procedures, and complications are significantly more likely in secondary procedures that may be necessary if there is a recurrence.
8.3.2.3 Recommendations for Extent of Surgery
In our opinion, it is important that patients with PTC be treated by a surgeon with extensive experience in performing total thyroidectomy. Despite the reported complications following total thyroidectomy, compli- cation rates are minimal in the hands of experienced surgeons [26] Furthermore, the high incidence of bi- lateral foci in patients with PTC indicates that these patients are best treated initially with total thyroid- ectomy, rather than undergoing a follow-up comple- tion thyroidectomy for recurrent or residual disease that was not appreciated at the primary evaluation.
Moreover, total thyroidectomy allows for more accu- rate follow-up using thyroglobulin as a marker of re- sidual or recurrent disease. Postoperative radioactive iodine scanning and ablation is also more effective in patients after total thyroidectomy compared with more conservative procedures. Finally, studies show that a lower recurrence rate and mortality are associ- ated with total or near-total thyroidectomy in patients with even low-risk PTC.
Thus, in virtually all patients, excluding those with the very best prognosis (tumor size less than 1 cm, confinement to the thyroid without metastases, in an otherwise healthy woman under 45 years of age), to- tal thyroidectomy is the treatment of choice for papil- lary thyroid carcinoma.
8.3.2.4 Lymph Node Dissection
As with any surgical procedure, lymph node dissec- tion carries some risk of iatrogenic injury. Specifically, nodal metastases in patients with PTC often requires
dissection in the proximity of the parathyroid glands, putting the glands at risk for injury secondary to sur- gical manipulation. Therefore, careful stratification of patients into groups requiring lymph node dissection and those not requiring lymph node dissection is im- portant for minimizing morbidity.
Approximately 80% of patients with PTC also have microscopic regional lymph node metastases [16].
The optimal diagnostic and therapeutic approaches for this have not been entirely clear. Microscopic oc- cult metastases may often be ablated by adjuvant ra- dioactive iodine therapy, but they may also be a site of persistent disease that would have easily been re- moved at the initial operation. While patients with PTC and matted lymph nodes or tumor extending through the lymph node capsule have a worse prog- nosis, the prognostic significance of lymph node me- tastases is controversial. [20,27,28].
Gross nodal disease occurs in 20–30% of adult cases of PTC, and is certainly justification for lymph node dissection (Fig. 8.3) [29]. Moreover, lymph node me- tastases are also associated with a higher recurrence rate when patients are matched for age and gender.
Therefore, nodal metastases confirmed by preopera- tive ultrasound or intraoperative exploration should be treated with node dissection [7]. Specifically, re- moval of ipsilateral central neck nodes and perithy- roid lymph nodes (Delphian node and lymph nodes medial to the carotid sheath) or lateral compartment nodes (levels 2–5) is important for nodes that have identifiable involvement with disease. Compartment- based resections of lateral neck nodes are preferable to “berry-picking” if they are clinically involved. For lateral compartment disease, the best approach is to perform functional modified radical neck dissection, during which all fibrofatty tissue with lymph nodes is removed. This procedure spares motor and sensory nerves, the sternocleidomastoid muscle, and the in- ternal jugular vein as well, unless they are involve by tumor.
Removal of central neck lymph nodes is associated
with an improvement in the regional recurrence rate,
and an improved survival rate in retrospective studies
[30–32]. This also has the advantage of demonstrat-
ing which patients have involved nodes, to make the
selection of radioiodine therapy clear, even for those
who may have otherwise apparently good prognostic
tumors (small size and lack of extrathyroidal exten-
sion). The current American Thyroid Association
Guidelines for the management of differentiated
thyroid cancer now call that a staging/prophylactic
level 6 lymph node dissection for all patients under-
going thyroidectomy for thyroid carcinoma should be
considered [33].
Prophylactic lateral neck node dissection is not recommended because in patients it is not associated with improved overall survival, and involves violation of additional planes by a substantially more extensive operation. However, follow-up of thyroid cancer pa-
tients by physical examination and ultrasound can identify patients with lateral neck nodal disease that can then be appropriately treated by therapeutic com- partmental node dissection (Fig. 8.4).
Fig. 8.3 Left cervical lymph node metastases detected on preopera- tive ultrasound examination of the neck (arrows). The node has the characteristics of replacement by metastatic disease, and was in- volved by FNA cytology. The node is globular and irregular in shape, compared to the typical smooth, fusiform node contour
Fig. 8.4 Metastatic cancer causing lymphadenopathy in the left neck of a teenaged woman with thyroid carcinoma. Detected upon fol- low-up examination, this enlarged, irregular node (arrows) led to a compartmental node dissection for metastases
8.3.3 Treatment: Follicular Thyroid Cancer
Despite differences in histological features, treatment for follicular thyroid carcinoma (FTC) is similar to that of PTC. Surgical resection remains the primary method of therapy for FTC of the thyroid. Moreover, the use of total thyroidectomy versus hemithyroid- ectomy is controversial. When dealing with disease confined to the thyroid (T1
–2 N0 M0), total thyroidec- tomy or hemithyroidectomy with extirpation of cen- tral lymph nodes are both adequate.
For larger tumors (T3–T4), more extensive therapy is warranted. Total thyroidectomy along with postop- erative radioactive iodine therapy is indicated in such cases. Proponents of unilateral procedures maintain that bilateral procedures carry an increased risk of morbidity, secondary to recurrent laryngeal nerve and parathyroid gland injury. Once again, morbidity is minimal in the hands of the experienced surgeon.
Since follicular tumors spread primarily via hema- togenous routes, cervical lymph node metastases are not as common in FTC when compared with PTC (35% versus 67%, respectively). However, therapeutic modified neck dissection is appropriate for patients with clinically apparent disease. Postoperative radio- active iodine scans and radioiodine ablation are also essential to help detect any residual disease and elimi- nate it.
8.3.4 Treatment: Oncocytic (Hürthle Cell) Thyroid Cancer
A variant of FTC, oncocytic carcinoma, is also known as oxyphilic or Hürthle cell carcinoma. While treat- ment strategies are similar to those of FTC, it is im- portant to distinguish the two entities. Radioactive iodine uptake in oncocytic carcinoma of the thyroid is much less than that of FTC, therefore, postopera- tive diagnosis and ablation of residual disease with radioactive iodine is more difficult in patients with oncocytic thyroid cancer. Because of similarities in the natural history and prognosis with FTC, treat- ment of oncocytic cell carcinoma is similar to that of FTC [34].
8.4 Risk Stratification for Cancer Treatment
Certain environmental and genetic factors play an important role in predisposing particular individuals
to developing thyroid cancer. Chances of developing differentiated thyroid cancers are increased by ex- posure to radiation. Such exposures occurred more often in the 1940s and 1950s than they do now. For instance, external radiation therapy was used to treat conditions such as tinea capitis, hypertrophic thymus, tonsillitis, acne, and otitis externa. Multiple studies have confirmed the increased risk of thyroid cancers and benign thyroid nodules in children exposed to low doses of radiation therapy [35–38]. It is impor- tant to note that exposure to external radiation beam therapy increases the risk of developing PTC, but it is not associated with the occurrence of FTC.
It has also been found that patients with familial adenomatous polyposis (FAP) have a predisposition toward developing benign and malignant thyroid neoplasms, specifically, differentiated tumors [39,40].
FTCs in particular have been associated with FAP, Gardner’s syndrome, and Cowden’s syndrome, but are most often sporadic.
Furthermore, studies have shown that diets both high and low in iodine can also increase the risk of developing thyroid cancer. When iodine uptake is sufficient, it is likely that a diagnosed differentiated thyroid carcinoma will be of the papillary type. FTCs are more common in areas that suffer from iodine deficiency and endemic goiter. Regions of the world suffering from iodine deficiency can exacerbate goi- ters by consumption of large quantities of cruciferous vegetables, which block iodine uptake [41].
Whereas certain environmental and innate fac- tors can influence one’s chance of developing thyroid cancer, the characteristics of a specific tumor or in- dividual can dictate the prognosis of the patient. The age at initial diagnosis, patient age, gender, and family history are all important factors in determining one’s prognosis. Specifically, increased recurrence rates are observed amongst patients under age 20 and over age 60. Moreover, mortality rates increase steadily after age 40 [42]. Nuclear atypia, tumor necrosis, vascu- lar invasion, and other characteristics of histological grade are also influential prognostic factors in pa- tients with thyroid cancer [43].
8.5 Summary
Thyroid nodules are quite common, and the basis of
their evaluation is the FNA cytology. However, some
tumors cannot be completely characterized by FNA,
and so require at minimum a diagnostic ipsilateral
thyroid lobectomy for definitive histology. In such
cases, complete lobectomy is the minimum proce- dure, to avoid the potential need for further operation on that side of the trachea.
Differentiated thyroid carcinoma is best treated by total thyroidectomy, which is safe in experienced hands. The best prognosis cancers can be managed by lobectomy alone with careful surveillance of the remaining lobe. Lateral neck dissection is reserved for clinically evident cancer involvement of that com- partment, though central neck (level 6) node dissec- tion should be a part of every initial thyroid cancer operation.
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