DIAGNOSIS OF SALIVARY GLAND TUMORS BY FNAC
GC Fernandes*, AA Pandit**
*Lecturer; **Professor, Dept. of Pathology, Seth GS Medical College, and KEM Hospital, Parel, Mumbai 400 012.
Fine needle aspiration cytology (FNAC) is being increasingly used in the diagnosis of salivary gland lesions. The aim of this study was to evaluate the diagnostic accuracy and efficacy of this procedure in various salivary gland tumours. A total of 123 FNAC’s were done on salivary gland tumours from January 1993 to July 1998 - a five and a half year period and the cytomorphological features were analysed. In the present series, the following lesions were studied; pleomorphic adenoma (64), monomorphic adenoma (6) Warthins tumour (1), mucoepidermoid carcinoma (5), acinic cell carcinoma (2) adenoid cystic carcinoma (2), malignant tumour (not specified) (1) and benign salivary gland lesion (42) respectively. Cytohistopathological correlation was available in 32 cases out of which 26 benign and 2 malignant were accurately diagnosed with an accuracy of 87.5%. There was 1 (3.12%) false positive and 3 (9.37%) false negative reports. Thus fine needle aspiration cytology is a useful diagnostic tool in evaluating neoplastic lesions of the salivary gland.
Although salivary gland tumours account for less than 3%  of all head and neck tumours, their superficial location, easy accessibility and high diagnostic accuracy make it a popular method for evaluating salivary gland tumours. It is also quite effective in the pre-operative evaluation of salivary gland masses.
The present study correlates the preoperative cytological picture obtained on FNAC with the histopathological features of surgically resected specimens. It also compares the results of this study with other studies. The purpose of the present study is to find out accuracy and usefulness of FNAC of salivary tumours.
MATERIAL AND METHODS
The usefulness of FNAC as a preoperative diagnostic procedure was studied in 123 patients with salivary gland tumours over a five and half year period from January 1993 to July 1998.
Patients with salivary gland masses were selected for pre-operative evaluation. The procedure was explained to the patients and the clinical data available was noted. The overlying skin was disinfected and FNAC performed with 22-33 guage needle with a 10 ml syringe. Multiple smears were prepared, fixed with 50% alcohol - 50% ether and stained with Papanicolau stain.
32 cases could be correlated with their histopathological findings and the results were compared. The overall diagnostic accuracy, sensitivity and specificity was calculated and compared with other studies.
TABLE 1 Cytodiagnosis of salivary gland tumours by aspiration biopsy Lesion No. of cases Percentage Pleomorphic adenoma* 64 52.04% Monomorphic adenoma 6 4.88% Warthin’s tumour 1 0.81% Mucoepidermoid carcinoma 5 4.06% Acinic cell carcinoma 2 1.63% Adenoid cystic carcinoma 2 1.63% Malignant tumour (not specified) 1 0.81% Benign salivary gland lesion (Neoplastic) 42 34.14% 123 100% * 3 cases showed epithelial hyperplasia.
TABLE 2 Comparison with other studies Various Authors No. of cases with histopathological confirmation Diagnosticaccuracy Sensitivity Specificity Shintani 43 93.00% 88.90% 94.10% Jayaram 57 87.70% 80.90% 94.30% Qizilbash 146 98.00% 87.50% — Cristallini-EG 63 97.90% 97.60% 98.45% MAVEC 475 87.80% 56.50% 98.90% Young 59 96.60% 87.50% 100.00% Bono 79 80.40% 85.70% 100.00% O’Dwyer 341 90.00% 73.00% 94.00% Our series 32 87.50% 90.30% 80.00%
TABLE 3 Correlation of cytodiagnosis with histopathology Histopathology Total Cytodi-
Mucoepider- moidcarcinoma Acinic Cellcar-
Adeno carcinoma (Low grade) Haema-
32 cases Pleomorphic adenoma
22 - 1 - - - 23 Mucoepid-ermoid carcinoma
- - 1 - - - 1 Acinic cell carcinoma
- - - 1 - - 1 Malignant tumour
- - - - - 1 1 Benign salivary gland lesion (Neoplastic)
3 1 - 1 1 - 6
There were 68 (55.29%) males and 55 (44/71%) females in this study. The parotid gland was involved in 64 (52.04%), the submandibular gland 55 (44.71%), submental 1 (0.81%) and others 3 (2.44%). There were 113 (91.87%) benign tumours and only 10 (8.13%) malignant tumours.
Out of the 32 cases which could be compared with the histopathological findings of the surgically resected specimens, there were 26 benign and 2 malignant accurately diagnosed giving a diagnostic accuracy of 87.5%. There was 1 (3.12%) false positive and 3 (9.37%) false negative reports.
Among the salivary glands, the parotid was the most commonly involved. Among benign tumours, pleomorphic adenoma 64 (52.04%) (Fig. 1) was the commonest and among malignant tumours, mucoepidermoid carcinoma 5 (4.06%) was common (Fig. 2). Most of the patients were in the 20-40 year age group and amounted to 57 (46.35%).
Out of the 23 cases of pleomorphic adenoma, 22 cases were correctly diagnosed thereby making FNAC quite helpful in the diagnosis of pleomorphic adenoma. The overall diagnostic accuracy
Fig 1 Pleomorphic adenoma.
Fig 2 Mucoepidermoid tumor.
was 87.5%, the sensitivity was 90.3% and the specificity was 80% which compares well with studies where the diagnostic accuracy ranged from 80.4% to 98%, sensitivity from 56.5% to 97.6% and specificity from 94% to 100%.
A few pitfalls in the diagnosis could not be avoided and 4 cases showed error in the diagnosis. One case of low grade mucoepidermoid carcinoma was diagnosed on cytology as pleomorphic adenoma. On reviewing the slides, the error was mainly due to limited sampling of material by the FNAC procedure. One case of low grade adenocarcinoma was labelled on cytology as benign salivary gland lesion (neoplastic) as the slides did not show any overt features of malignancy. The other two cases, one of which was an adenoid cystic carcinoma which was labelled on cytology as benign salivary gland lesion (neoplastic) and the other which was a haemangioma was misdiagnosed as a malignant tumour (not specified). Errors in the diagnosis mainly occurred in cases of low grade malignant tumours.
In view of the ever increasing health costs, FNAC of salivary glands provide financial advantages by providing rapid and accurate diagnosis on an OPD basis.
We conclude that FNAC is an important and useful diagnostic tool in the pre-operative assessment of patients with salivary gland masses.
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