Benign follicular thyroid lesions versus follicular variant of papillary carcinoma: differentiation by architectural pattern

Differentiation between benign and malignant follicular lesions is one of the difficult diagnostic areas in thyroid fine needle aspiration (FNA). Nuclear criteria are usually used to distinguish between them. In this study the microarchitectural pattern of common benign follicular lesions, namely nodular hyperplasia (NH) and follicular adenoma (FA) were analysed in comparison with those of follicular variant of papillary carcinoma (FVPC) in order to aid in their differentiation. The FNA smears of histologically proven cases of FVPC, NH and FA were reviewed and compared. The microarchitectural features of FVPC, NH and FA were described. Three cytological features--multi-layered rosettes, branching monolayered sheets and balls of thick pinkish colloid--were exclusively observed in FVPC. Hyperplastic papillae with intact follicles and colloid were frequently seen in NH, 83% and 100%, respectively. Albeit less frequently, they were also noted in FVPC, 25% and 75% of cases, respectively. These overlapping features make the distinction between FVPC and NH sometimes difficult; however, assessing the smears for the specific features of FVPC may help in their differentiation. None of the aforementioned microscopic findings with the exception of the seldom presence of colloid were documented in FA. The crowded clusters of follicular cells were seen both in FA and FVPC; however, they were complex and branching in the latter and round to oval in the former. Finally, smears with good recovery of material are indispensable for the identification of these helpful microarchitectural patterns.     

Is a five‐category reporting scheme for thyroid fine needle aspiration cytology accurate? Experience of over 18 000 FNAs reported at the same institution during 1998–2007

S. Piana, A. Frasoldati, M. Ferrari, R. Valcavi, E. Froio, V. Barbieri, C. Pedroni and G. Gardini Is a five‐category reporting scheme for thyroid fine needle aspiration cytology accurate? Experience of over 18 000 FNAs reported at the same institution during 1998–2007 Objective: Fine needle aspiration (FNA) has long been recognized as an essential technique for the evaluation of thyroid nodules. Although specific cytological patterns have been recognized, a wide variety of reporting schemes for thyroid FNA results have been adopted. This study reports our experience with a five‐category reporting scheme developed in‐house based on a numeric score and applied to a large series of consecutive thyroid FNAs. It focuses mainly on the accuracy of thyroid FNA as a preoperative test in a large subset of histologically distinct thyroid lesions. Methods: During the 1998–2007 period, 18 359 thyroid ultrasound‐guided FNAs were performed on 15 269 patients; FNA reports were classified according to a C1–C5 reporting scheme: non‐diagnostic (C1), benign (C2), indeterminate (C3), suspicious (C4), and malignant (C5). Results: Non‐diagnostic (C1) and indeterminate (C3) FNA results totalled 2 230 (12.1%) and 1 461 (7.9%), respectively, while suspicious (C4) and malignant (C5) results totalled 238 (1.3%) and 531 (2.9%), respectively. Histological results were available in 2 047 patients, with thyroid malignancy detected in 840. Positive predictive value of FNA was 98.1% with a 49.0 likelihood ratio (LR) of malignancy in patients with a C4/C5 FNA report. Conclusions: This five‐category scheme for thyroid FNA is accurate in discriminating between the virtual certainty of malignancy associated with C5, a high rate (92%) of malignancy associated with C4, and a 98% probability of a histological benign diagnosis associated with C2. Further sub‐classifications of C3 may improve the accuracy of the diagnostic scheme and may help in recognizing patients eligible for a ‘wait and see’ management.     

Fine needle aspiration cytology of primary lymphoma of the thyroid: a report of 17 cases.

Between 1980 and 1998, 4272 thyroid surgical specimens with a preoperative fine needle aspirate were sent to our Anatomical Pathology Department. Among these cases there were 17 primary thyroid lymphomas, which constituted 0.3% of all the thyroid lesions and 2.3% of the thyroid malignancies. Seven cases were diffuse large B-cell (DLBC) lymphomas and 10 were MALT lymphomas. Of the DLBC lymphomas six were correctly diagnosed by fine needle aspiration cytology (FNAC) and one was diagnosed as positive for malignancy, and among MALT lymphomas four were diagnosed as lymphoma, four as suspicious for lymphoma, and three as Hashimoto's thyroiditis (HT). Our data indicate that the diagnosis of primary thyroid lymphoma of high grade is easy, and immunocytochemistry (ICC) can confirm suspicious cases. The diagnosis of MALT lymphoma is more difficult; ICC can confirm suspicious cases, and false-negative results seem to be caused by sampling error, because HT usually coexists with MALT lymphoma.     

The role of liquid-based cytology in the investigation of thyroid lesions

Objective:  This study investigates the role of liquid-based cytology by ThinPrep^® technique in the detection of thyroid lesions.
Methods:  In all, 252 specimens from 157 patients for pre-operative evaluation of thyroid nodules, prepared by the ThinPrep^®, were examined. In all cases thyroidectomy followed the initial cytological evaluation. All cytological diagnoses were correlated to the histological ones.
Results:  According to our findings, a sensitivity of 87.80%, a specificity of 99.50%, a positive predictive value of 97.30%, a negative predictive value of 97.56% and an overall accuracy of 97.52% were observed in fine needle aspiration cytology in correlation to the histological diagnosis after thyroidectomy.
Conclusions:  ThinPrep^® technique is a valid method for the pre-operative cytological diagnosis of thyroid nodules, offering the possibility of ancillary techniques, such as immunocytochemical and molecular methods and can, therefore, be potentially complementary to histological evaluation for further investigation of follicular lesions.     

Fine needle aspiration cytology of the thyroid: a comparison of 5469 cytological and final histological diagnoses

OBJECTIVE: We evaluated the efficacy of fine needle aspiration cytology (FNAC) of the thyroid in a series of 5469 lesions with histological control and studied the causes of, and the possibility of reducing the limitations of the method. METHODS: FNAC was always performed by a pathologist under the guidance of a clinician, using a 22-gauge needle. Generally two aspirations were carried out, and usually four slides were obtained for each nodule; they were then stained with May-Grünwald-Giemsa and with Papanicolaou. The cytological diagnoses were classified in four groups: inadequate, benign, suspicious and malignant. RESULTS: We obtained a complete sensitivity of 93.4%, a positive predictive value of malignancy of 98.6%, and a specificity of 74.9%. At histological control, the cytological diagnosis of Hurthle cell neoplasm corresponded to a significantly higher incidence of malignant neoplasms than the diagnosis of non-Hurthle cell follicular neoplasm (32.1% versus 15.5%). There were 66 false-negative findings, the main cause of diagnostic error (24 cases) being failure to recognize the follicular variant of papillary carcinoma. The number of inadequate FNACs was low (4.2%). CONCLUSION: Our study confirmed the great efficacy of thyroid FNAC. A cytological diagnosis of Hurthle cell neoplasm should be considered an indicator of high risk. Awareness that failure to recognize the follicular variant of papillary carcinoma was the main problem in the interpretation of thyroid FNAC should lead to a decrease of false-negative diagnoses. The inadequate rate was very low, as it was the pathologist personally who performed the needle aspiration.     

Fine needle aspiration cytology of thyroid nodules: how accurate is it and what are the causes of discrepant cases?

Fine-needle aspiration cytology (FNAC) is widely accepted as the most accurate, sensitive, specific and cost-effective diagnostic procedure in the assessment of thyroid nodules and helps to select people preoperatively for surgery. The purpose of this study was to evaluate the results of thyroid FNAC in our institution and to determine the reasons for discrepancies between the cytological and histological diagnosis. We evaluated the cytological and histological results of 254 FNACs obtained from 231 patients who underwent subsequent thyroid surgery. All of the material was blindly reviewed for quality control, by one experienced cytopathologist. All FNACs were carried out under ultrasound guidance. The cytological diagnosis was classified as benign, suspicious, malignant or unsatisfactory. The definitive histological study showed benign lesions in 195 of the 231 patients (84%). A benign diagnosis based on FNAC was correct in 105 of the 108 benign cases (97%). FNACs diagnosed as 'suspicious' resulted in a distribution of 49 benign (79%) and 13 malignant (21%) diagnoses. FNAC showed malignancy in 34 cases (13%) and in only one case did the final histology differ from cytology (correlation 97%). The percentage of FNACs that were inadequate for diagnosis was 20%. Review of cytological and histological slides did not lead to any change in the original diagnosis. Our study revealed a cytological-histological discrepancy (2%) in only 4 out of 231 cases over a period of 10 years, due to either a diagnostic or sampling error.     

Thyroid fine needle aspiration cytology processed by ThinPrep: an additional slide decreased the number of inadequate results

E. D. Rossi, F. Morassi, G. Santeusanio, G. F. Zannoni and G. Fadda
Thyroid fine needle aspiration cytology processed by ThinPrep: an additional slide decreased the number of inadequate results Background: Fine needle aspiration cytology is the most accurate tool for diagnosing thyroid nodules. Its accuracy is related to the rate of inadequate samples, which can be minimized with the adoption of on‐site assessment of the adequacy of the material. The introduction of liquid‐based cytology (LBC) in the thyroid does not allow checking on the adequacy of the cellularity. The possibility of making a second LBC slide for decreasing the number of non‐diagnostic cases is studied. Methods: Out of 553 cases diagnosed in a single institution from January to March 2005, 166 consecutive cases with an LBC slide reviewed by the same pathologist were evaluated. The cases were classified in a five‐tiered category system (Thy1 to 5 according to the British Thyroid Association guidelines) and all but two (with cystic degeneration) were processed by LBC and stained with Papanicolaou stain. The above‐mentioned categories are defined as follows: Thy1 inadequate or haemorrhagic, Thy2 non‐neoplastic lesion; Thy3 follicular lesion/suspected follicular neoplasm; Thy4 suspicious for malignancy; Thy5 diagnostic of malignancy. For each case the cytological diagnosis was made on the LBC slide and the adequacy of the cellularity for a conclusive diagnosis was assessed. Results: Of the 166 cases, 39 were non‐diagnostic (Thy1—inadequate), ten presented features of cystic degeneration (Thy1—haemorrhagic), 90 were benign (Thy2), 22 were diagnosed as a follicular lesion (Thy3), one as suspicious of malignancy (Thy4) and four as papillary carcinoma (Thy5). Thirty‐nine cases had a second LBC for achieving a definitive diagnosis with eventual re‐classification. Of these cases, 23 (61.5%) led to a conclusive diagnosis (18 Thy2, five Thy3) with a 18.5% decrease of the inadequacy rate. Conclusions: The making of an additional LBC slide helps in achieving a diagnosis in cases classified as non‐diagnostic on the first standard slide (52.1% recovery rate). This procedure is particularly helpful for meeting the adequacy criteria in benign and indeterminate lesions and could also be used for refining the diagnosis of suspicious for a malignant thyroid neoplasm.     

Fine needle aspiration cytology in non-neoplastic non-toxic recurrent nodular goitre

The aim of the study was to examine whether evaluation of anisokaryosis is helpful in the cytological diagnosis of focal lesions in non-toxic recurrent goitre (NRG) after thyroidectomy for non-malignant goitre. Karyometric analysis was performed in routine cytological smears obtained from 80 females: 40 with focal lesions in non-toxic primary goitre (NPG) and 40 with NRG (postoperative histopathological examination revealed nodular goitre in both groups in all cases). We found that the level of anisokaryosis was significantly (P<0.005) higher in NRG than in NPG. There were no significant differences between the two lesions, in cellular composition or thyroid follicular cell arrangement. Thus, isolated anisokaryosis, a feature of malignancy in patients without a prior thyroidectomy, has limited diagnostic value in recurrent goitre.     

Immunocytochemical detection of Ki‐67 in Diff‐Quik‐stained cytological smears of canine mammary gland tumours

U.S. Choi and D.Y. Kim Immunocytochemical detection of Ki‐67 in Diff‐Quik‐stained cytological smears of canine mammary gland tumours Objective: To investigate whether Diff‐Quik stained fine needle aspirate smears can be used to evaluate Ki‐67 expression by immunocytochemistry. Methods: Both cytological and histological samples were obtained from 24 dogs with spontaneously developed mammary gland tumours. The cytological and histological specimens were examined by Diff‐Quik and H&E stains, respectively. After examination, both samples were immunostained using the same Ki‐67 antibody. The % Ki‐67 values were calculated based on the percentage of positively stained tumour cells per 500 and 1000 tumour cells in cytology and histology specimens, respectively. Results: Ki‐67 staining was successful in 17/24 smears (71%) and 19/23 sections (83%). The correlation coefficient between the percentage of Ki‐67‐positive cells in cytological smears and in the histological sections was 0.677 (P < 0.01). These values were significantly different between histologically benign and malignant tumour groups both in cytology and histology samples (P < 0.001). The threshold value of the percentage of Ki‐67‐positive cells for distinguishing benign from malignant tumours was set at 4.85% with 90.9% sensitivity and 92.3% specificity by Receiver Operating Characteristic (ROC) curve using histopathology as the gold standard. Conclusion: Diff‐Quik‐stained cytology smears can be used to detect the presence of Ki‐67 antigen when histology sections are not available.     

Effect of ultrasound transmission gel on ultrasound‐guided fine needle aspiration cytological specimens of thyroid

A. Lalzad, D. Ristitsch, W. Downey, A. F. Little and M. E. Schneider‐Kolsky
Effect of ultrasound transmission gel on ultrasound‐guided fine needle aspiration cytological specimens of thyroid Objective: To investigate prospectively the diagnostic impact of ultrasound coupling gel on thyroid specimens obtained under ultrasound guidance. Methods: Patients presenting for ultrasound‐guided fine needle aspiration (USG‐FNA) of the thyroid were invited to participate in the study. Four specimens per nodule were collected: two using chlorhexdine wash and two using sterile, colourless ultrasound gel as couplant according to routine protocol. All slides were analysed in a blinded fashion by two senior cytologists for the presence or absence of ultrasound gel‐induced artefacts. The presence of gel‐induced artefacts between the two groups was analyzed using Pearson’s chi‐square test. Kappa statistics were used to measure the inter‐rater agreement between the cytologists. Results: Twenty thyroid nodules comprising 80 specimen slides were collected. On slides collected with gel, cytological artefacts were detected in 60–65% of cases compared with 10–15% of cases without gel (P < 0.001). The inter‐rater agreement between the two observers was very good (κ = 0.84). Two of the 14 patients required repeat FNA due to non‐diagnostic cytology results caused by inadequate sampling and gel‐induced artefacts. Conclusions: Clinical cytopathologists, radiologists and sonographers should be aware of the potential for ultrasound gel to cause significant artefacts on cytological specimens. Our findings suggest that staff involved in USG‐FNA cytology should remove the gel carefully before taking the aspirate.