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ORIGINAL ARTICLE  
Year : 2018  |  Volume : 61  |  Issue : 1  |  Page : 45-49
Liquid-based cytology versus conventional cytology in fine-needle aspirates of salivary gland neoplasms


Department of Pathology, King George's Medical University, Lucknow, Uttar Pradesh, India

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Date of Web Publication22-Mar-2018
 

   Abstract 


Background: Liquid-based cytology (LBC) is a method of retrieving and processing of cytological material for the assessment of both gynecological and nongynecological cases introduced in 1996. Mostly conventional smears (CS) are prepared in Indian scenario; however, due to increasing popularity of LBC in nongynecology specimens, LBC is also used in few centers for diagnosing salivary gland neoplasm. Aim: The aim of this study is to compare CS and LBC in fine-needle aspiration cytology (FNAC) of the salivary gland neoplasms in terms of cytomorphological details, adequacy, ease of interpretation, pitfalls, and diagnostic efficiency. Materials and Methods: We conducted a prospective, observational, comparative study which included 64 salivary gland neoplasms. Both CS and LBC (SurePath) were prepared as per standard protocols and examined. Results and Conclusion: In our study, specificity and positive predictive value of both the techniques (conventional and LBC) were found to be 100%. Sensitivity of both the techniques was found to be similar (66.7%). Negative predictive value and diagnostic accuracy of conventional technique were found to be almost similar to that of LBC technique (97.6% vs. 97.2% and 97.7% vs. 97.4%). In terms of adequacy and cellularity, CSs were better than LBC. Ease of interpretation was better with CSs due to abundant chondromyxoid stroma, an important clue in the diagnosis of pleomorphic adenoma. Nuclear details and background were better in LBC as compared to CS. Hence, we conclude that in salivary gland FNAC, both CS and LBC have similar diagnostic efficiency. however, interpretation of conventional smears is easier than Liquid Based Cytology especially in cases of pleomorphic adenoma. However, some advantages of LBC in respect to conventional cytology, with better-preserved morphology obtained from LBC becomes furthermore obligatory.

Keywords: Conventional cytology, fine-needle aspiration cytology, liquid-based cytology, salivary gland neoplasms

How to cite this article:
Kumar M, Katiyar S, Sagar M, Kumari M, Goel MM. Liquid-based cytology versus conventional cytology in fine-needle aspirates of salivary gland neoplasms. Indian J Pathol Microbiol 2018;61:45-9

How to cite this URL:
Kumar M, Katiyar S, Sagar M, Kumari M, Goel MM. Liquid-based cytology versus conventional cytology in fine-needle aspirates of salivary gland neoplasms. Indian J Pathol Microbiol [serial online] 2018 [cited 2019 Dec 6];61:45-9. Available from: http://www.ijpmonline.org/text.asp?2018/61/1/45/228189





   Introduction Top


Tumors of the salivary gland comprise 3%–6% of all the head and neck neoplasms in adults with an incidence of 1–3/100,000 people/year. Fine-needle aspiration (FNA) biopsy is a well-established diagnostic procedure. It is widely used to evaluate palpable lesions and with the aid of imaging studies is equally applicable to deep-seated lesions.[1],[2] FNA cytology of the salivary gland is an accepted, sensitive, and specific technique in the diagnosis of both nonneoplastic and neoplastic lesions.[3] However, salivary gland lesions remain, one of the most challenging entities in cytopathology, mainly because of the diversity of histologic subtypes and the often overlapping morphologic features of the lesions.[4] Liquid-based cytology (LBC) as a technique was introduced and tried on  Pap smear More Detailss. It received the Food and Drug Association approval in 1996.[5] Thereafter, this technique has been used for nongynecological cytology, including conventional FNA cytology (FNAC), guided FNAC, and fluid cytology.

Aim and objectives

To assess the diagnostic efficacy of LBC (SurePath) versus conventional cytology in fine-needle aspirates of salivary gland neoplasms and to compare cytomorphological features in conventional FNA and LBC smears from salivary gland neoplasms. To analyze the results of both techniques in terms of following: cellularity, adequacy, interpretation, concordance, pitfalls, and diagnostic efficiency.


   Materials and Methods Top


This study was conducted in the department of pathology, in collaboration with department of ear, nose, and throat of our medical university. This is observational comparative study of two cytopreparatory techniques in the 1-year duration. Direct alcohol-fixed FNAC smears were stained using hematoxylin and eosin stain and Papanicolaou stain and air-dried smears with May-Grunwald Giemsa stain for conventional smears (CS). Follow the “Non-Gyn Slide Processing” instructions in the BD PrepStain™ Operator's Manual for proper slide preparation. Both CS and LBC (SurePath) were prepared as per the standard protocols. All CS and their corresponding LBC smears were examined by two cytopathologists independently.

Statistical analysis was done using Statistical Package for the Social Sciences Version 15.0 statistical analysis softwarE SPSS inc.,2006, Chicago, USA. The values were represented in number (%) and mean ± standard deviation. The following statistical formulas were used mean, standard deviation, Chi-square test, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and level of significance (P value).

Our study has been approved by the ethical committee of King George's Medical University, Lucknow.


   Results Top


A total of 64 salivary gland neoplasms were enrolled in the study who reported to our department. Most of the patients presented between 3rd and 5th decade of life. Out of 64 cases, 48 (75.00%) were found to be benign and rest of the 16 (25.00%) were found to be malignant. None of the malignant case was aged up to 20 or 21–30 years of age. Out of 48 benign cases, 47 (97.9%) were pleomorphic adenoma and rest 1 (2.08%) case was of Warthin's tumor. Out of 16 malignant cases, 11 (68.7%) cases were of mucoepidermoid carcinoma (MEC) and 1 (6.3%) case each of adenoid cystic carcinoma, Acinic cell carcinoma, oncocytic carcinoma, salivary duct carcinoma, and carcinoma ex-pleomorphic adenoma. Cellularity was found to be better in CS in majority of cases (n = 31; 60.8%) while cellularity in 5 (9.8%) cases were found to be better in LBC technique. The results of rest 15 cases (29.4%) were found to be almost similar by both the techniques. Therefore, conventional technique was found to be better with respect to cellularity in majority of the cases.

Architecture was better seen in CS (n = 33; 64.7%) as compared to LBC (n = 2; 3.9%). Nuclear details were better in LBC technique as compared to CS (84.3% vs. 1.96%). The results of nuclear details in both the techniques were found to be similar in 7 (13.7%) cases. Cytoplasmic details of 33 (64.7%) cases were found to be similar by both the techniques while better results by LBC technique were obtained in 12 (23.5%) cases and better results by conventional technique were obtained in 6 (11.8%) cases.

Chondromyxoid stroma was better observed by conventional technique in 34 (66.7%) cases, whereas in rest, 17 (33.3%) cases results of conventional and LBC technique were found to be similar. Background details were better observed in all the cases by LBC technique. Ease of interpretation was better by conventional technique as compared to LBC (68.6% vs. 19.6%). The results of both the techniques were found to be similar in 6 (11.8%) cases [Table 1].
Table 1: Cytomorphological details of parameters observed in liquid-based cytology and conventional cytology

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Proportion of cases with concordance with histopathological diagnosis was higher in conventional technique (93.2%) as compared to those with LBC technique (79.5%). No comments on the results of 6 cases by LBC technique could be made due to the inadequacy of samples in LBC technique. Difference in concordance with histopathological diagnosis by both the techniques was not found to be statistically significant and was due to the inadequacy of samples in LBC [Table 2]. Comparison of histological diagnosis, conventional cytology and LBC was available in 38 cases only due to nonavailability of histology in some cases and inadequacy of samples in LBC in other cases.
Table 2: Concordance of conventional and liquid-based cytology with histopathological diagnosis (n=44)

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Out of 34 cases of histologically proven pleomorphic adenoma, 100% cases were diagnosed correctly by both the techniques; however, ease of diagnosis was more with conventional technique (76.5%) as compared to LBC (8.8%). This was mainly due to the presence of abundant chondromyxoid stroma and good cellularity in CS. Chondromyxoid stroma was altered in both quantity and quality in LBC. In case of histologically proven Warthin's tumor, diagnostic efficacy was similar in both the techniques; however, ease of interpretation was greater with LBC due to better nuclear and cytoplasmic details. In case of the salivary duct and oncocytic carcinoma which were diagnosed on histopathology, both the techniques did not diagnose them accurately [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d. In one case of histologically proven MEC both the techniques diagnosed it as benign. In 7 cases of MEC, no histology was available since they presented in advanced stage and were advised radiotherapy. Diagnostic efficacy was similar in both the techniques; however, ease of diagnosis was more with LBC (57.1%) as compared with CS (42.8%). Rest 3 cases of MEC were inadequate in LBC. One case of adenoid cystic carcinoma was also advised radiotherapy. Diagnostic efficacy was similar in both the techniques; however, the interpretation was better by LBC [Figure 2]a,[Figure 2]b,[Figure 2]c,[Figure 2]d. A case of acinic cell carcinoma did not get operated, and hence, no histology was available. Both the techniques diagnosed it accurately; however, ease of interpretation was better with CS [Figure 3]a and [Figure 3]b. Of the 38 cases, in which diagnosis by both liquid-based technique and histopathology could be established, all the cases except 1 case matched with that of histopathological diagnosis. That 1 case diagnosed to be malignant by the histopathological technique was diagnosed as benign by the LBC and conventional cytology technique.
Figure 1: (a and b) Conventional smears and liquid-based cytology smear of pleomorphic adenoma (May-Grunwald Giemsa, ×10 and Pap, ×20). (c and d) Conventional smear and liquid-based cytology smear of Warthin's tumor (H and E, ×20 and Pap, ×20)

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Figure 2: (a and b) Conventional smears and liquid-based cytology smear of mucoepidermoid carcinoma (H and E, ×20 and Pap, ×20). (c and d) Conventional smear and liquid-based cytology smear of adenoid cystic carcinoma (May-Grunwald Giemsa, ×20 and Pap, ×20)

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Figure 3: (a and b) Conventional smears and liquid-based cytology smear of acinic cell carcinoma of (H and E, ×20 and Pap, ×20)

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The sensitivity, specificity, PPV and NPV, and histopathology were taken as the gold standard. Specificity and PPV of both the techniques (conventional and LBC) were found to be 100%. Sensitivity of both the techniques was found to be similar (66.7%). NPV and diagnostic accuracy of conventional technique were found to be comparable to that of LBC technique (97.6% vs. 97.2% and 97.7% vs. 97.4%) [Table 3]. Therefore, in both CS and LBC have similar diagnostic efficiency, however, ease of interpretation in salivary gland tumors, especially pleomorphic adenoma is better with CS as compared to LBC due to better visualization of chondromyxoid stroma, better architectural details, and better cellularity.
Table 3: Comparison of sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of conventional and liquid-based cytology technique

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   Discussion Top


Salivary gland tumors account for 2%–6.5% of all the head and neck tumors, their superficial location, easy accessibility, and high diagnostic accuracy makes FNAC a popular method for evaluating them.[6] The introduction in 1996 of LBC has gained enthusiasm as a new technique for collection and preparation of cytological specimens, first in cervical cytology and then with the application on FNAC with reliable and feasible results.[7]

The purpose of the current study is to compare the diagnostic accuracy and morphology of LBC (SurePath) and conventional cytology in the salivary gland FNAC in a total of 64 cases. In the present study, benign lesions accounted for 48/64 (75%) of the cases while malignant lesions accounted for 16/64 (25%) of the cases. Males were affected more than females, and this finding was supported by other Indian studies.[8],[9]

The most common benign lesion was pleomorphic adenoma (47/48; 97.9%) and the most common malignant lesion was MEC (11/16; 68.7%) which was similar to the study done by Anand et al.[8]

In the present study, parotid gland was most commonly affected (49/64) followed by submandibular gland (10/64) and minor salivary glands (5/64). This finding was in agreement with other studies like Vikram et al.[10] and Jain et al.[11]

In terms of adequacy, CSs were found to be adequate in all benign and malignant cases while LBC was adequate in 39/48 benign cases and 12/16 malignant cases. This was also seen in other studies like Parfitt et al.[12] where the reason of inadequacy was use of split sample technique. In this study, two separate passes were made for CS and LBC. The material aspirated in the first pass was smeared on slides for conventional cytology. The material aspirated in the second pass was rinsed in preservative fluid for LBP. Inadequacy in LBC could have occurred due to sampling error or due to decanting procedure of SurePath. In SurePath, centrifugation is done two times and the material is decanted during which loss of cells may have occurred and also loss of cellularity may have occurred during the second pass if the needle did not strike the site of lesion or due to hemorrhage after the first pass. There is also a pitfall in the technique of SurePath where the material is decanted after centrifugation during which loss of material can occur.

Cellularity was better in CSs in 31/51 (60.8%) cases, equal in both techniques in 15/51 (29.4%) cases while cellularity was better in LBC in 5/51 (9.8%) cases. This was concordant with the study done by Hoda,[13] in which cellularity was lower in LBP as compared to conventional preparation. According to this study, in FNA cases where LBC were prepared from needle and syringe rinse after initial CS preparation, significant loss of cells was seen.

Architectural arrangement was better in CS (33/51; 64.7%) as compared to LBP (2/51; 3.9%). In CS, cells were seen arranged in sheets, large aggregates, and papillary clusters, whereas in LBP, there was fragmentation of cells into smaller groups along with an increase in number of singly scattered cells. The cell size was smaller in LBC as compared to CS.

Chondromyxoid stroma in cases of pleomorphic adenoma, the most common diagnosis in salivary gland neoplasms, was seen better in 34/51 (66.7%) cases of CS, whereas in 17/51 (33.3%) cases, it was equal in both the techniques. However, in none of the cases, it was better in liquid-based preparation. In literature, it is reported that background matrix is altered in both quantity and quality in liquid-based preparation. However, most of the studies have been done on ThinPrep technique. In SurePath, the loss of extracellular elements is less pronounced.[13]

The above findings were concordant with other studies like Tripathy et al.,[14] Rarick et al.,[15] Hipp et al.,[16] Ren et al.,[17] Mygdakos et al.,[18] Parfitt et al.,[12] Hoda,[13] Al-Khafaji and Afify,[19] and Michael and Hunter.[20]

Biscotti et al.[21] compared LBC and CS in thyroid aspirates and reported similar diagnostic accuracy with both techniques, although they pointed out that colloid was decreased and appeared as droplets in liquid-based preparations.

Nuclear details and cytoplasmic details were well preserved in LBC. In the present study, nuclear details were seen better in LBC as compared to CS [Table 1]. This was concordant with studies such as Parfitt et al.[12] and Leung et al.[22] nucleocytoplasmic ratio was well preserved in LBC.

Rana et al. conducted a study on respiratory cytology specimens and found no difference in the diagnostic accuracy between LBP and CS; they did, however, favor LBP over CS because of a cleaner background, more even cell distribution, and better cell preservation in the former.[23] These results are similar to the present study, where less obscuring blood, no crush or air-drying artifacts, and better nuclear details were observed with LBP.

In terms of ease of interpretation, pleomorphic adenoma was more easily diagnosed in CS due to better cellularity and chondromyxoid stroma in CS than in LBC smears. However, in a single case of Warthin's tumor, ease of diagnosis was more in LBP due to better nuclear and cytoplasmic details. In MEC, 4/7 cases were diagnosed with ease in LBP as compared to 3/7 cases in CS. In case of adenoid cystic carcinoma, ease of interpretation was more with LBC while acinic cell carcinoma was more easily diagnosed with CS. However, the evaluation of specific diagnosis in malignant category was limited in our study due to relatively low number of cases in each category. We also had a single case of carcinoma ex pleomorphic adenoma but its LBP was inadequate, therefore, interpretation was not possible.

In this study, specificity and PPV of both the techniques (conventional and LBC) were found to be 100%. Sensitivity of both the techniques was found to be similar (66.7%). NPV and diagnostic accuracy of conventional technique were found to be almost similar to that of LBC technique (97.6% vs. 97.2% and 97.7% vs. 97.4%).

These findings were concordant with the study done by Hipp et al.[16] in 2015. They concluded that the absolute cytohistologic concordant rate for the positive cases (type of neoplasms specified) was similar between the two preparations (80% vs. 86%; P = 0.354). Furthermore, there was no significant difference in rate of accurate diagnosis (correct typing of benign versus malignant neoplasm) between the two preparations (70% vs. 81%; P = 0.057).

However, LBC is superior to CS in terms of nuclear details, clear background, and loss of obscuring artifacts. Therefore, LBC may be considered as another practical method of specimen preparation in the assessment of salivary gland neoplasms.

According to the study done by Parfitt et al.[12] although CS appears to be preferable to LBP in the diagnosis of pleomorphic adenoma overall, CS and LBC have equivalent diagnostic yield in highly cellular cases. Therefore, complementary use of both LBP and CS preparations is recommended to achieve optimal diagnostic yield, given the artifacts of some CS and the not infrequent unsatisfactory nature of one preparation alone.

Evaluation of specific diagnosis in this study was limited by relatively low numbers of cases in each category. Histological correlation was not available in all the cases as some patients with malignant lesions who presented in advanced stage were advised radiotherapy while others did not get operated or were lost to follow-up. Evaluating LBP requires experience with the process; therefore, it is important to train the pathologists using a set of cases prepared by both LBP and CS before implementing the practice for patient care. The interpretation requires familiarity with the appearance and artifacts of liquid-based cytology in the various types of preparations to avoid misdiagnosis.


   Conclusion Top


In terms of adequacy and cellularity, CSs were better than LBC. Ease of interpretation was better with CSs due to abundant chondromyxoid stroma, an important clue in the diagnosis of pleomorphic adenoma. Nuclear details and background were better in LBC as compared to CS. Hence, in salivary gland FNAC, both CS and LBC have similar diagnostic efficiency. However, interpretation of conventional smears is easier than Liquid Based Cytology especially in cases of pleomorphic adenoma. However, some advantages of LBC in respect to conventional cytology, it is less time-taking technique, well-preserved cytomorphology of cells with clear background.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Cajulis RS, Gokaslan ST, Yu GH, Frias-Hidvegi D. Fine needle aspiration biopsy of the salivary glands. A five-year experience with emphasis on diagnostic pitfalls. Acta Cytol 1997;41:1412-20.  Back to cited text no. 3
    
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Hoda RS. Non-gynecologic cytology on liquid-based preparations: A morphologic review of facts and artifacts. Diagn Cytopathol 2007;35:621-34.  Back to cited text no. 13
    
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Tripathy K, Misra A, Ghosh JK. Efficacy of liquid-based cytology versus conventional smears in FNA samples. J Cytol 2015;32:17-20.  Back to cited text no. 14
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Correspondence Address:
Madhu Kumar
Department of Pathology, King George's Medical University, Lucknow - 226 003, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJPM.IJPM_729_16

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