BACKGROUND: Fine-needle aspiration remains the primary diagnostic intervention for the evaluation of most thyroid nodules larger than 1-1.5 cm. Although most aspirates provide diagnostic cytology, approximately 15-25% will be classified indeterminate (often referred to as follicular neoplasm, suspicious for carcinoma, or atypical). In such cases, abnormal cellular findings preclude interpretation of benignity, although only a minority will prove cancerous upon final histopathology. Nonetheless, patients with indeterminate aspirates are commonly referred for consideration of hemi- or near-total thyroidectomy.Recently, improved understanding and novel investigation of clinical, radiological, cytological, and molecular factors has allowed improved stratification of cancer risk.

CONCLUSION: Although surgery continues to be commonly recommended, strategies for such patients should increasingly seek to define treatment based on the estimation of an individual's thyroid cancer risk in comparison with associated operative risk and morbidity. In doing so, the rate of unnecessary surgical procedures and associated complications can be reduced.

Department of Molecular Medicine and Surgery, Karolinska University Hospital, 171 76, Stockholm, Sweden. cia.ihre-lundgren@ki.se

BACKGROUND: Since the development of fine-needle aspiration biopsy (FNAB) techniques, preoperative diagnosis and subsequent strategies for patient treatment have changed and evolved greatly. This is true also for thyroid FNAB: the vast majority of thyroid nodules are benign, and hence do not necessarily require surgical treatment.
 

METHODS: A comprehensive Medline and Cochrane Library search was performed evaluating FNAB in the thyroid. In the last decade more than 400 articles on the  subject have been published. Data in relation to the experience with FNAB at the  Karolinska University Hospital since its introduction were also reviewed.
 

RESULTS: The development of FNAB since the 1960s at the Karolinska University Hospital is described. During the period 1992-1996 the accuracy of the clinical routine was evaluated by studying the outcomes of almost 4,000 FNAs of the thyroid. The results were good, with only a few false-negative and false-positive results, but the problem of differentiating follicular adenoma from follicular carcinoma remained a significant problem. The use of immunological analysis has greatly increased the possibility of obtaining valuable information on cellular characteristics.
 

CONCLUSION: A successful FNAB service rests on several factors, and the importance of clinical conferences between all specialists involved in the diagnosis and treatment of patients with thyroid disorders cannot be overemphasized. At the Karolinska University Hospital there are weekly conferences where patients are discussed both pre- and postoperatively. These conferences lead to optimal interaction between the different specialists and, most important, substantial improvement in the clinical management of patients with thyroid disorders.

BACKGROUND: Subclassifying indeterminate thyroid fine-needle aspiration (FNA) biopsy findings as follicular lesion or follicular neoplasm has been suggested as useful in triaging patients to observation or surgery, respectively. However, terminology and therefore the probability of malignancy vary between pathologists and institutions. The purpose of this study was to evaluate a single institution's experience with indeterminate thyroid FNA results to determine if subclassification (neoplasm versus lesion) aids in identifying patients at higher risk for malignancy.
 

METHODS: From 1990 to 2006, all patients with indeterminate thyroid FNA results (follicular lesion or neoplasm) at The University of Texas M.D. Anderson Cancer Center were evaluated for FNA correlation with the surgical specimen diagnosis. Patients with FNAs suspicious for papillary thyroid carcinoma or with definitive malignant disease (i.e., metastases) were excluded.
 

RESULTS: Indeterminate FNA results were present in 540 patients, including 410 as follicular lesion and 130 as follicular neoplasm. Two hundred ninety-seven (55.0%) patients underwent surgical resection: 199 (48.5%) follicular lesions and 98 (75.4%) follicular neoplasms. Incidence of malignancy was higher in thyroid nodules classified as neoplasm compared with lesion (21.4% versus 7.0%, respectively; P=0.0005) and increased in follicular neoplasms with nodule size (37.5% malignant if nodule was [4 cm, P=0.03).

CONCLUSIONS: Subclassification of indeterminate thyroid FNA biopsy results into neoplasm and lesion successfully defines high- and low-risk nodules, respectively. These findings support surgical resection for follicular neoplasms, selective use of surgical intervention for follicular lesions at our institution, and continued efforts to define unified terminology between institutions.

Most thyroid neoplasms arise from follicular cells and are well differentiated. Anaplastic and poorly differentiated carcinomas are rare and have a high mortality. Five percent of tumors are of C-cell origin, and 20% to 25% of these are hereditary. Thyroid lymphoma is rare and occurs in the setting of Hashimoto's thyroiditis. Fine needle aspiration biopsy is the best diagnostic tool to