6.2 Review of Literature
Miller et al (1979)1 compared the accuracy of specimens obtained by fine and large needle biopsy of 1094 nodules previously evaluated by clinical methods.
They reported that 42 of 47 excised cancers were included in the cytohistological probable cancer group and all 51 excised cytohistologically benign nodules were benign. They stated that FNA can be used as a screening procedure for all nodules. Whenever possible, obtaining cutting needle biopsy and aspiration needle biopsy specimens adds on additional dimension to diagnostic precision and reduces the potential for sampling error.
They also stated that in terms of cost effectiveness, cytohistological diagnosis has the important advantages of greater economy and specificity when compared with the less decisive conventional clinical workup and the greater cost and morbidity of diagnostic lobectomy.
Lowhagen et al (1979)2, evaluated the accuracy of FNAC in the diagnosis of malignant thyroid tumours. 412 patients who underwent primary operation of thyroid lesions suspected to be malignant, in whom thyroid FNAC had been performed preoperatively were included in the study.
They reported that FNAC gave no false positive reports as regards malignancy and false negative results occurred in 2.2% .They stated that FNAC is a safe and accurate method for establishing whether a thyroid nodule is benign or malignant. Diagnostic operations were avoided in many patients. They also stated that when there is a clinical suspicion of malignancy, one should proceed with surgical exploration despite a negative cytological diagnosis.
Gita jayaram (1984)3, correlated 308 solitary nodules subjected to FNAC with histopathology. The accuracy of FNAC in the diagnosis of adenomatous goitre was 95.8%,accuracy of benign tumours was 100%. Although follicular carcinomas were diagnosed with a low accuracy of 21.1%, aspiration cytology did correctly diagnose the presence of neoplastic lesion in 94.7% cases.
The author stated that the findings reconfirmed the overall utility of FNAC in the specific diagnosis of most of the thyroid lesions. The author recommended FNAC as a valuable adjuvant to preoperative screening in the diagnosis of thyroid nodules.
Giuseppe Altavilla et al (1990)4, examined 2433 lesions of the thyroid gland by FNAC. Cytopathology classified 66.91% of the aspirates as benign, 10.76% as thyroiditis, 4.89% as suspected neoplasms, 1.31% as positive for malignancy and16.11% as unsatisfactory. They compared the FNAC diagnosis of 257 cases of thyroid gland diseases with the histologic diagnosis to determine the accuracy.
The study yielded a sensitivity of 71.43%, specificity of 100% and an accuracy of 95.09%. They recommended thyroid FNA as an important preoperative diagnostic tool. Follicular carcinomas were difficult to cytologically differentiate from nonmalignant follicular neoplasms and papillary thyroid carcinomas less than 2 cm in diameter and in elderly patients, were frequently misdiagnosed only as “suspect lesion”.
Klime et al (1991)5 compared 194 cases of thyroid nodules which were aspirated with histopathology and autopsy findings (3 cases). 3% of the cases with a cytology diagnosis of benign, 20% of cases with an FNAC diagnosis of suspicious and 100% of cases with FNAC diagnosis of malignancy were histologically malignant.
They reported that FNAC has a diagnostic specificity of 100% , sensitivity of 55% FNAC and accuracy of 95%. They concluded that FNAC is a practical method with considerable diagnostic value in the evaluation of thyroid nodules.
Martinek et al(2004) 6aim of the study was to assess the accuracy and limitations of ultrasound guided fi ne-needle aspiration cytology
( FNAC) of thyroid nodules. Usg-FNAC results of 245 patients with thyroid nodules, who afterwards underwent thyroid surgery or who died, and autopsies were carried out, and compared retrospectively with cytologic results. Patients with malignant
cytologic conclusion without histological confirmation after surgery or autopsy were excluded from the study (9 persons). Usg-FNAC results were divided as follows: group 1: diagnosis of malignancy (n = 30), group 2: suspicion of malignancy (n = 28), group 3: benign (n =126), group 4: inconclusive (n = 29).
Results: Assuming the cytologic results of group 1 and group 2 were interpreted as being malignant and those of group 3 as being benign, the sensitivity, specifi city and accuracy of Usg-FNAC were 90 %, 85 % and 86 % respectively.
Comparing the cytologic conclusions between a group of patients with follicular lesions and a subgroup of other lesions a statistically significant difference (p < 0,01) between both subgroups using Fisher’s test was found. Sensitivity, specificity and diagnostic accuracy in subgroup of follicular lesions were low (71 %, 63 %, 67 %), while in the subgroup of other lesions were high (94 %, 86 %, 88 %). FNAC can specify the nature of focal lesion with high sensitivity, specifi -
city and diagnostic accuracy in the cases of non-follicular lesions. Histological evaluation is required to specification of the nature in cases in which cytology is indicative of follicular proliferation
Tzu chi (2008)7aim of this study was to evaluate the results of thyroid fine needle aspiration cytology (FNAC) and identify reasons for discrepancies between the cytological and histological diagnoses . evaluated the results of 1064 FNACs obtained from 737 patients, of which 98 underwent subsequent thyroid surgery. Histological analyses revealed that benign diagnoses based on FNAC were correct in 76 of the 80 benign cases (95%), with four cases being underdiagnosed (false negatives). Two of the four cases were due to incidental findings of papillary microcarcinomas. The third case was due to a cytologic sampling error and the fourth was due to cytologic underdiagnosis. Furthermore, malignant diagnoses based on FNAC were correct in 17 of the 18 malignant cases (94%), with one case being over-diagnosed (false positive) due to over-interpretation of Hürthle cells as carcinomatous cells. The accuracy, positive predictive value, and negative predictive value were 94.9%, 94.4%, and 95.0%, respectively. They concluded FNAC as a sensitive and specific method for the pre-operative screening of thyroid nodules. However, due to limitations under some specific circumstances, such as papillary microcarcinoma, bizarre Hürthle cells, follicular neoplasm and technical difficulty during the aspiration, the management of thyroid nodules must not only depend on the results of FNAC but should also be correlated with clinical findings before surgical intervention.
Rabia basharat et al (2011) 8 comparative study between FNAC and thyroid scan used to diagnose the solitary thyroid nodule and histopathology was used as gold standard to compare the results of both modalities. We hypothesized that Fine needle aspiration cytology and thyroid scan diagnose solitary thyroid nodule (STN) as accurately as histopathology. This study comprised of 50 patients with solitary thyroid nodules (STN) . On thyroid scan, 40 patients (80%) having cold nodule were labeled as suspicious 10 patients (20%) had hot nodule. On FNAC 23 patients (46%) had benign lesion, 22 patients (44%) had indeterminate lesion and 5 patients (10%) had malignant lesions. On histopathology, 45 patients (90%) were confirmed to have benign lesions and 5 patients (10%), malignant lesions. After comparison of results of thyroid scan and FNAC with histopathology, the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of thyroid scan were 80%, 20%, 10%, 90% and 26%, respectively whereas those of FNAC were 80%, 97.7%, 80%, 97.7% and 96%, respectively. Conclusion. Fine needle aspiration was a significantly better predictor of malignancy than thyroid scan and resulted in a smaller proportion of excisions for benign nodules