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Management guidelines for patients with thyroid nodules

Thyroid nodules are common. Up to 5% of the population have a palpable nodule and on ultrasound, 50% of the population will have subclinical thyroid nodules. Of these, approximately 5% will be malignant. Management of thyroid nodules to reliably diagnose malignant lesions and enable conservative treatment of benign nodules is important; especially because of an increasing incidence in thyroid cancer. In this issue of the journal, Raj et al. highlight the importance of synoptic cytology reporting for fine needle aspiration biopsy of thyroid nodules. A clearly defined management algorithm for thyroid nodules and, in particular, a detailed understanding of the implications of a thyroid fine needle cytology report, is critical to successful management of the patient with a thyroid nodule. These principles have recently been summarized in the revised American Thyroid Association Management Guidelines for patients with thyroid nodules and differentiated thyroid cancer. A thorough clinical assessment of the patient, including a history of childhood head and neck irradiation, a family history of thyroid cancer or a thyroid cancer syndrome, rapid growth, hoarseness, vocal cord paralysis, cervical lymphadenopathy and fixation of the nodule to surrounding tissues, will increase the likelihood of a malignant diagnosis. All patients should undergo an estimation of thyroid stimulating hormone (TSH) and if suppressed, should have thyroid scintigraphy. Hot nodules should not be subjected to fine needle aspiration cytology as they are likely to be cellular and falsely positive for a suspicious lesion. Hyper-functioning nodules are rarely malignant. All patients should undergo diagnostic thyroid ultrasonography. Suspicious sonographic features include: micro-calcifications, hypoechoic nodules, irregular margins, internal vascularity, loss of a halo and increased height to width ratios. All nodules greater than 1 cm in size should be evaluated; however, nodules less than 1 cm in diameter, which are incidentally discovered on ultrasound, also require evaluation if there are suspicious ultrasound findings, associated lymphadenopathy, history of head and neck irradiation or a history of thyroid cancer. Serum calcitonin will be a useful adjunct in the setting where medullary thyroid cancer is suspected on the basis of a family history of MEN2 syndrome or the presence of diarrhoea or cytological features such as prominent spindle cells which may suggest the diagnosis. A positive pre-operative diagnosis of medullary thyroid cancer will facilitate one stage total thyroidectomy and appropriate management of the cervical lymph nodes as outlined in this journal in the paper by Abraham et al. Fine needle aspiration cytology is the most accurate and cost effective method for evaluating thyroid nodules; ultrasound guidance increases the accuracy of the result and reduces the nondiagnostic rate. In the past, multiple diagnostic categories of fine needle aspiration biopsy results were utilized but these have more recently become categorized into synoptic groups which determine management A consensus paper on synoptic cytology reporting from the National Cancer Institute Thyroid Fine Needle Aspiration State of the Science Conference, has recently been published. A tiered system of cytology reporting aids the clinician in management. It is essential that the clinician and cyto-pathologist have a good concordant and mutual understanding of the implications of the report. However, the cytology report does not provide a diagnosis in itself, but rather categorizes a nodule into a group, which, in association with the clinical features and ultra-sonographic features, enables a management decision to be made. A non-diagnostic sample indicates the need for a repeat aspiration. A benign cytological aspirate, indicating a colloid or hyperplastic or adenomatous nodule, carries a very low risk of malignancy – less than 5% false negative. These patients can be observed with ultrasound assessment of size at 12 months. A malignant cytological diagnosis is at least 95% accurate and may definitively diagnose papillary thyroid cancer, medullary thyroid cancer, and anaplastic carcinoma, metastases and lymphoma. Definitive surgery can be based on this result. Suspicious cytology carries a risk of malignancy of 50–75%; samples typically contain some but not all features of papillary thyroid cancer. Such a pattern is often seen in the follicular variant of papillary thyroid cancer. Because of the advantages of one-stage surgery, namely one anaesthetic one operation, the ability to stage the neck lymph nodes preoperatively and plan lymph node dissection and avoiding the increased difficulties of a second operation, it is appropriate to pursue a malignant diagnosis in this group. For this reason, it is often useful to obtain further opinions about a suspicious cytological aspirate or to repeat the aspirate, either or both of which may ultimately give a definitive malignant diagnosis. The indeterminate follicular group represents a mixture of cytological results and is variously reported by different groups. Cytology results indicating a follicular neoplasm or Hurthle cell neoplasm mandate diagnostic hemithyroidectomy to establish a potential diagnosis of invasive follicular cancer, which can only be diagnosed by evidence of capsular and/or vascular invasion. An indeterminate follicular lesion, where a colloid or hyper-plastic nodule is favoured over a follicular neoplasm, requires an overall decision about management to be made on the basis of a combination of the cytology, EDITORIAL