The role of thyroid fine needle aspiration (FNA) cytology in a District General Hospital setting

Role of Scrape Cytology as an Adjunct to Fine Needle Aspiration Cytology in Diagnosis of Thyroid Lesions

INTRODUCTION

Scrape cytology is an important diagnostic tool. It has been used in many tissue types as an adjunct or replacement for frozen section/ intra operative consultation.

AIM

This study was done to evaluate the role of scrape cytology in the diagnosis of thyroid lesions, its role as an adjunct to Fine Needle Aspiration Cytology (FNAC) and application of this technique for intra-operative consultation.

MATERIALS AND METHODS

A prospective study on 50 thyroid neoplasms received over a period of 18 months (Nov 2014- March 2016) was conducted. Scrapings obtained from the fresh cut surface of thyroid specimens before formalin fixation, were smeared uniformly on to glass slides, and immediately fixed in 95% ethyl alcohol for rapid Haematoxylin and Eosin (H&E). Cytological findings were compared with pre-operative FNAC findings and histopathological diagnosis. Variables taken in to consideration while assessing the smears included cellularity, nuclear, cytological details and amount of colloid.

RESULTS

There were total of 50 patients. Out of the 50 patients, 15 were diagnosed as benign on scrape; of which 100% of cases were true negative for malignancy and five malignant cases were diagnosed as benign-false negative rate of 16.1%; four (8%) were deferred (non-diagnostic) with a true positive rate of 83.3%. Histopathological correlation was available in all cases. The overall diagnostic accuracy of scrape cytology was 89.1% with sensitivity and specificity of 83.87% (C.I.; 66.27% to 94.55%) and 100% (C.I; 76.84% to 100.00%) respectively. Fine Needle Aspiration results were available in 41 cases of which 2 were non-diagnostic. Of the remaining 39 cases 19 were benign and 20 were malignant with false negative rate of 40% and true positive rate of 60%. The overall diagnostic accuracy of FNAC was 64.1% with sensitivity and specificity of 60% (C.I.; 40.6% to77.3 %) and 77.78% (C.I; 39.9% to 97.1%) respectively.

CONCLUSION

We conclude that scrape cytology can act as a useful adjunct to FNAC and is a good procedure for intra-operative consultation. It is especially helpful in neoplasms diagnosed as suspicious for papillary carcinoma on aspiration and may obviate the need for a second procedure for completion thyroidectomy.

Basics of cytology

This overview is intended to give a general outline about the basics of Cytopathology. This is a field that is gaining tremendous momentum all over the world due to its speed, accuracy and cost effectiveness. This review will include a brief description about the history of cytology from its inception followed by recent developments. Discussion about the different types of specimens, whether exfoliative or aspiration will be presented with explanation of its rule as a screening and diagnostic test. A brief description of the indications, utilization, sensitivity, specificity, cost effectiveness, speed and accuracy will be carried out. The role that cytopathology plays in early detection of cancer will be emphasized. The ability to provide all types of ancillary studies necessary to make specific diagnosis that will dictate treatment protocols will be demonstrated. A brief description of the general rules of cytomorphology differentiating benign from malignant will be presented. Emphasis on communication between clinicians and pathologist will be underscored. The limitations and potential problems in the form of false positive and false negative will be briefly discussed. Few representative examples will be shown. A brief description of the different techniques in performing fine needle aspirations will be presented. General recommendation for the safest methods and hints to enhance the sensitivity of different sample procurement will be given. It is hoped that this review will benefit all practicing clinicians that may face certain diagnostic challenges requiring the use of cytological material.

Ultrasound-guided fine-needle capillary biopsy of thyroid nodules, coupled with on-site cytologic review, improves results

Fine-needle aspiration biopsy represents the most reliable test for cytologic evaluation of thyroid nodules. However, inadequate samples may occur leading to a repetition of the procedure with the consequence of patients' discomfort and poor compliance. In this paper, we present results from biopsy of thyroid nodules obtained by combining: (1) ultrasound (US) guidance, (2) no-aspiration technique, and (3) on-site review of specimens. A total of 465 nodules were biopsied in 307 patients. Solitary nodules and multinodular goiter were present in 36.8% and 63.1% of patients, respectively. After collection, each sample was smeared in duplicates, one of which was stained with hematoxylin and checked on-site by a cytopathologist. In cases of inadequate smears, biopsies were immediately repeated. All slides were then processed for final cytologic results, which were reported as benign in 427 nodules (91.8%), malignant in 12 nodules (2.5%), with follicular proliferation or suspicious for malignancy in 23 nodules (4.9%). Inadequate final cytology was reported in 3 nodules (0.6%). No statistically significant relationship was found between nodule size and adequacy of specimens. We conclude that the combination of US guidance, capillary collection with no-aspiration technique, and on-site review of slides, characterizes an advantageous method for thyroid nodule fine-needle biopsy.

An alternate model of thyroid cytology: practical not perfect

A sample of 384 thyroid cytology specimens prepared by cytospin over a 2.5-year period was classified by original report into inadequate, non-neoplastic and suspicious of neoplasia or worse. This was then compared with subsequent histology. The resulting data showed an inadequacy rate of 33%, a sensitivity of 55%, a specificity of 59%, a positive predictive value of 64% and a negative predictive value of 93%. On review of the cytology, in knowledge of the subsequent histology, the maximum achievable results were determined to have a positive predictive value of 79% and a negative predictive value of 97%. No clinically significant adverse event was detected.

Screening high-risk populations for thyroid cancer

BACKGROUND

Children treated with radiotherapy to the neck or exposed to environmental radiation are at risk for developing thyroid cancer later in life. The best method for screening these high-risk patients is unclear. We systematically reviewed evidence on the accuracy of ultrasound and palpation to detect thyroid nodules and of fine needle aspiration (FNA), a confirmatory test, to diagnose thyroid cancer.

PROCEDURE

We searched the MEDLINE database for papers published since 1966, using the MeSH term thyroid neoplasms and terms related to diagnostic test performance. To supplement our MEDLINE searches, we searched reference lists from recent reviews and articles recommended by thyroid cancer experts. We recorded the tests used, the gold standard determination of disease, the test performance results, and the presence of biases that could affect the reported results. We also abstracted the number of patients who underwent surgery and the final diagnoses. We created two decision models: one for screening 10,000 medically irradiated patients, and one for screening 10,000 environmentally irradiated patients.

RESULTS

Using ultrasound as the gold standard determination of the presence of a nodule, the sensitivity of palpation for all sized nodules was 10-41 percent, indicating that a high proportion of nodules detected by ultrasound are too small to be palpated. Sensitivity of palpation increased with nodule size. The specificity of palpation ranged from 95 to 100%. In studies from referral centers, the reported sensitivity and specificity of FNA were 71-95 and 52-99%, respectively. However, most authors excluded the proportion of patients (6-33%) who had inadequate or nondiagnostic FNA results when calculating sensitivity and specificity, even though 6-100% of these patients went on to have a diagnostic lobectomy. When each study was reanalyzed so that patients with nondiagnostic FNA results who went directly to surgery were reclassified as positive tests, sensitivity increased slightly, but specificity dropped by 4-20 percentage points per study. The decision model for screening 10,000 medically irradiated patients revealed that if ultrasound were used as an initial screen, 2,741 patients would have nodules at least 1 cm in size; assuming no patients with smaller nodules had surgery, 1,964 patients would have surgery; 275 patients would have a diagnosis of thyroid cancer. Screening with ultrasound as an initial test would detect an additional 150 cases of thyroid cancer compared to those screened with palpation. However, an additional 1,689 patients would have surgery for nonmalignant nodules (compared to 480 patients with nonmalignant nodules screened with palpation). The yield for screening 10,000 environmentally irradiated patients was several times smaller than for screening 10,000 medically irradiated patients. If 10,000 environmentally irradiated patients were screened initially with ultrasound, approximately 708 patients would have nodules at least 1 cm in size; 89 patients would have surgery; and 38 patients would be diagnosed with thyroid cancer.

CONCLUSIONS

Regardless of type of exposure, testing initially with ultrasound detects several times more cases of thyroid cancer than palpation. However, when ultrasound is the initial test, many more patients also have surgery for nonmalignant nodules. Screening with palpation is not very reassuring, particularly to medically irradiated patients with negative tests, since almost half (46%) of these patients may have undetected nodules.

Thin layer compared to direct smear in thyroid fine needle aspiration

The efficacy of preparing thyroid fine needle aspirations (FNAs) by the thin layer as opposed to the direct smear method has not been evaluated sufficiently in a regional laboratory setting. At the Foothills Hospital (Calgary, Canada), the method of processing thyroid FNAs was changed from direct smear to thin layer in January 1996. The results of 327 patients who had direct smear from 1994 to 1995 were compared to 401 who had thin layer between 1996 and 1997. While there were no significant differences across a broad range of quality indicators, thin layer showed a trend towards a higher proportion of true benign diagnoses (31% vs 24%), a lower proportion of inadequate specimens (41% vs 50%) and, most importantly, a lower false negative rate (3% vs 9%). In conclusion, the changeover to thin layer did not compromise the interpretation of thyroid FNAs.

The role of fine needle aspiration cytology (FNAC) in the investigation of superficial lymphadenopathy; uses and limitations of the technique

Aspirates (n = 163) from 157 patients with enlarged superficial lymph nodes were obtained over a 5-year period in a combined surgical/FNAC clinic. A definitive diagnosis was achieved in over 77% of the cases: benign 52.7%, malignant 25.1%. The diagnostic accuracy was 94.4%, sensitivity 85.4%, and specificity 100%. The false-negative rate was 12.5% but decreased to 3.5% when lymphoma cases were excluded. There were 36 cases of metastatic disease, the majority of which were from a primary breast carcinoma. The main diagnostic difficulty was in distinguishing low-grade lymphoma from reactive hyperplasia. An added advantage was that aspirated material could be used in ancillary tests to help with the differential diagnosis. FNAC has a well-defined role in the investigation of superficial lymphadenopathy. Used in the proper setting it will provide a definitive diagnosis in the majority of cases, especially relating to recurrent malignancy or metastatic disease. Patients with a reactive cytological picture and no clinically suspicious symptoms could be spared unnecessary surgery and reviewed through follow up. This technique is cost-effective, of high diagnostic accuracy, and results in considerable resource savings.

Detection of telomerase expression in fine-needle aspirations and fluids

The cytologic examination of fine-needle aspirates and fluid specimens is plagued by a persistent false negative rate. The rate of false negative results will be decreased if sensitive molecular assays can be developed to detect cytologically malignant cells. The current study investigated telomerase expression as a potential marker of malignancy, using the telomeric repeat amplification protocol (TRAP) in fine-needle aspirates and fluid specimens. TRAP was performed on 24 fine-needle aspirate and 24 fluid specimens from different body sites and of different histological diagnoses. We found that 6 of 12 fine-needle aspirate specimens that were cytologically positive for malignant cells expressed telomerase activity, while no specimens that were cytologically suspicious for malignancy, atypical, or negative tested positive for telomerase activity. Of the fluid specimens, 4 of 6 cytologically positive cases and 1 of 18 cytologically negative cases expressed telomerase. Seven of eight telomerase negative, cytologically positive specimens contained only rare malignant cells in a very bloody background. Peripheral blood contamination is a possible pitfall in the TRAP assay, as applied in the current study, because the assay is standardized to protein concentration that may be derived from lysed red blood cells. We conclude that with further technical refinement, the TRAP assay could become a useful adjunct in the cytologic examination of fine-needle aspirates and fluid samples.