Presentation of Clinically Solitary Thyroid Nodules in Surgical Patients

Introduction

T hyroid nodules are very common, with prevalence rates of 50%–60% at autopsy (1,2). The diagnosis of thyroid incidentalomas is also increasing with detection rates of 16% by computed tomography and magnetic resonance imaging scans (3), 9.4% by carotid duplex scans (4), 67% by ultrasonography (5), and 2%–3% by positron emission tomography scans (6). The prevalence of clinically palpable thyroid nodules in the general population, however, is only about 4%–7% (7,8). Approximately 80% of solitary thyroid nodules are due to colloid nodules, simple thyroid cysts, or thyroiditis. Of the remainder, 10%–15% are benign follicular adenomas, and only 5% are thyroid carcinomas (9). In Australia, the commonest type of clinically solitary thyroid nodule seen in clinical practice is a dominant colloid nodule within a multinodular goiter, where the remainder of the gland is not palpable (10).

The thyroid gland, due to its anatomical location in the anterior triangle of the neck, is one of the few parts of the body where clinically obvious pathology may not be directly observed by the patient but may readily be apparent to others. Indeed the anterior aspect of the neck is a conspicuous region, which is perpetually on display in most people for most of the day. For this reason, third-party diagnosis, usually by a friend or family member, is well recognized by clinicians as a common source of referrals for the investigation of thyroid nodules. Another unique characteristic of the thyroid gland is its tendency to move with swallowing. This provides further opportunities for an informed observer to reach a confident clinical diagnosis.

While many medical textbooks and journal articles discuss the mode of presentation of thyroid nodules, the evidence supporting these data is largely anecdotal. A literature search of several databases and search engines, including MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, American College of Physicians (ACP) Journal Club, Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials, and PubMed, on common modes of presentation of thyroid nodules, yielded no results, suggesting that there is a lack of published data to support the widely accepted statements noted above. The detection of thyroid incidentalomas, however, is extremely well documented (11 –15), despite continuing controversy regarding their management. Most textbooks and journal articles also stipulate that differences exist between modes of presentation of benign versus malignant thyroid nodules, once again with limited supporting evidence.

The aim of this study was to evaluate the prevalences of the various initial presentations of the solitary thyroid nodules that eventually come to the practice of surgeons. It was also to assess whether or not the presence of thyroid cancer impacted upon the mode of initial presentation.

Materials and Methods

Results

There were 419 patients in the initial study cohort. Of that group, no documentation on mode of presentation could be found in the records of 69 patients and these were excluded. A further 51 patients underwent surgery for their thyroid nodule as part of a parathyroid operation where the primary indication was hyperparathyroidism, so these were also excluded, leaving a final study cohort of 299 patients. This comprised of 59 men and 240 women. The age distribution was 52.6 ± 17.59 for men and 50.9 ± 17.32 for women; 184 patients underwent an open hemithyroidectomy or partial thyroidectomy, while 115 underwent a minimally invasive thyroid procedure. The final pathology is summarized in Table 1. Of the entire group, thyroid cancer was demonstrated in 56 patients (18.7%).

Table 2 summarizes the differing modes of clinical presentation. In relation to third-party presentations, 89 (29.8%) thyroid nodules were actually detected by a third party with the patient having been entirely unaware of the presence of the nodule before it was pointed out to them. Of that group, 26 were noted by non-medical observers, including family members (13 cases), most commonly by the patient's mother, friends (6 cases), and acquaintances (7 cases) such as a beautician, a massage therapist, a herbalist, an osteopath, a midwife, a singing teacher, and a member of a television audience. The remaining 63 in the third-party group were noted by medical practitioners, most commonly the patient's general practitioner (GP) undertaking a routine check-up and less commonly a medical specialist seeing the patient for some other disorder.

Imaging studies or blood tests picked up 90 (30.1%) previously undetected solitary thyroid nodules. Ten patients had nodules detected subsequent to the investigation of abnormal thyroid or parathyroid function tests. Three of these patients had hyperthyroidism, two had subclinical hyperthyroidism, two had hypothyroidism, two had fluctuating thyroid function tests, and one patient had hyperparathyroidism. The different imaging modalities include Sestamibi scans, usually performed before parathyroidectomy (5.4%), plain X-rays (2.7%), duplex and regular ultrasonography (10.0%), computed tomography scan (7.4%), positron emission tomography scan (0.3%), magnetic resonance imaging (0.7%) and Barium swallow (0.3%). Curiously, patients with thyroid incidentalomas found on imaging studies, tended to be much older (mean age 61.1 ± 15.65 years) than patients who noticed the nodules themselves (mean age 47.1 ± 15.52 years) and patients in whom the diagnosis was made by a third party (mean age 46.8 ± 17.40 years). The fact that older people have coexisting health issues that warrant imaging may account for this finding.

The commonest mode of presentation involved incidental discovery of the thyroid nodule by the patients themselves (120 cases, 40.1%), with the majority of these (72 cases, 24.1%) presenting as palpable swellings in the neck without local pressure symptoms. The rest presented with local obstructive symptoms (10.4%) such as dysphagia, dysphonia and shortness of breath, or symptoms of hyperthyroidism (5.7%) requiring further investigation. Mode of presentation may relate to the size of clinically solitary thyroid nodules with patient-noted nodules (29.06 ± 15.41 mm) being larger than those observed by a third party (24.13 ± 15.21 mm), which were in turn, slightly larger than incidentalomas (21.11 ± 12.52 mm) detected on imaging (Table 2).

Table 3 summarizes the various presentations in relation to final pathological diagnosis. Clinically solitary thyroid nodules incidentally detected by medical practitioners were more likely to harbor a malignancy (p = 0.02) than nodules presenting in other ways. Of note, malignant nodules tended to be slightly smaller on average, 19.83 ±16.64 mm, than benign nodules, with Follicular and Hurthle cell adenomas measuring 29.49 ± 14.76 mm and dominant nodules in a multinodular goiter averaging 24.71 ±13.36 mm. Lastly, the mean age for people with benign nodules (50.85 ± 16.68 years) was no different to the mean age of those with malignant nodules (49.13 ± 15.87 years). Hence benign and malignant nodules appear to be clinically indistinguishable.

Discussion

It is a commonly acknowledged fact that solitary thyroid nodules are often diagnosed incidentally due to the thyroid gland's prominent position in the anterior triangle of the neck. Several well-known textbooks of endocrinology state that most thyroid nodules are asymptomatic, and are therefore discovered incidentally, by the patient themselves, by a third party known to the patient, by physicians, or on imaging studies (16,17). One textbook goes on to stipulate that local discomfort is more likely in a malignant nodule (16), whereas other textbooks state that benign and malignant nodules cannot adequately be differentiated on symptoms and signs alone (18). Most journal articles state that solitary thyroid nodules present as asymptomatic nodules incidentally palpated by a physician or by the patient, without any evidence to support this statement (13,19 –22) other than one retrospective study from Singapore (23), which states that thyroid nodules most commonly present as a neck lump with no further information regarding their precise mode of discovery.

Our study examined a highly selected group of patients with thyroid nodules who subsequently underwent surgery and, therefore, represents only a small percent of the entire population of people with thyroid nodules. Therefore, the mode of presentation of thyroid nodules as reported in this study is not representative of the way in which thyroid nodules present at a community level. Nonetheless, it provides interesting information regarding the way in which solitary thyroid nodules are brought to the attention of medical practitioners.

In Australia, the interest surrounding third-party diagnosis of thyroid nodules peaked a few years ago when an observant viewer noticed a thyroid nodule in an Australian TV personality, and several newspapers and women's magazines ran articles on the subject. However, while such third-party diagnosis of thyroid nodules on television makes for interesting reading, thyroid nodules are diagnosed in a variety of ways.

The mode of presentation of clinically solitary thyroid nodules can be divided into three main groups: (a) discovered by patients themselves, (b) third-party diagnoses, and (c) diagnoses made on imaging studies performed for an unrelated reason. The results of this study show that the largest proportion of patients with clinically solitary thyroid nodules presented of their own accord (40.1%), either due to the incidental palpation of an asymptomatic thyroid nodule or with symptoms of local pressure or hyperthyroidism.

Most patients who noticed the nodule themselves had no local pressure symptoms and discovered the nodule while idly palpating their neck, brushing their teeth, or shaving. Of the symptomatic group, the majority presented with local obstructive symptoms such as shortness of breath, cough, dysphagia, and an increasingly hoarse voice. A minority presented after the sudden onset of a painful lump, due to haemorrhage into the nodule. Many patients also presented with symptoms of hyperthyroidism, though not a single patient in this study presented with symptoms of hypothyroidism, perhaps because the symptoms of hypothyroidism are so nonspecific.

The increasing discovery of incidentalomas in the thyroid, adrenal, and pituitary glands due to the advent of newer technologies is a well-documented phenomenon (11 –15). Hence, it is not surprising that patients with incidentalomas comprised the second largest group (30.1%) in our study. Further, this group of patients were older than the patients in each of the other groups, a statistic that may be explained by the fact that older people have concomitant health issues and are therefore more likely to undergo imaging studies.

Third-party diagnoses made by family, friends, acquaintances, or physicians composed the smallest of the three groups (29.8%), with the majority of these being made by medical practitioners, most commonly the patient's own GP. GPs usually made these incidental discoveries during a routine check-up, or less commonly when the patient presented for evaluation of an upper respiratory tract infection. The remaining incidental diagnoses were made by medical practitioners from a variety of fields, including endocrinologists (usually treating the patient for diabetes), cardiologists, obstetricians, gastroenterologists, urologists, and physicians in the emergency department. Clinically, solitary thyroid nodules detected by medical practitioners were statistically more likely to be malignant (p = 0.02), although this may simply represent selection bias.

No correlation was found between the size of thyroid nodules and the incidence of malignancy. However, larger nodules were more likely to be detected by the patients themselves, whereas smaller nodules were more likely to be picked up on incidental imaging. Lastly, the mean age of those with benign and malignant nodules was the same. Previous studies suggest that certain clinical features are more likely to be associated with malignancy. These include an iodine-deficient diet, a history of radiation exposure, a positive family history of thyroid cancer, male gender, a fixed or enlarging nodule, cervical lymphadenopathy, and vocal cord paralysis (19,24). However, our study aimed to determine whether there was any difference in mode of presentation between benign and malignant disease, specifically to determine whether malignant nodules are more likely to present symptomatically. According to our study, benign and malignant solitary nodules are clinically indistinguishable at presentation, and require further investigation by ultrasonography, fine needle biopsy, and even surgical excision as indicated by the surgeon's clinical judgement.

In conclusion, while the incidence of thyroid incidentalomas is well documented, information regarding other modes of presentation is largely anecdotal. Several textbooks and journal articles currently express mixed views regarding the primary mode of presentation of clinically solitary thyroid nodules. Our study conclusively establishes that it is the patient who plays the most important role in the incidental discovery of clinically solitary thyroid nodules.