Introduction
Fine needle aspiration cytology is a minimally invasive procedure that has been widely accepted in the evaluation of lesions in thyroid, lymph nodes and salivary gland, to name a few. 1, 2 Salivary gland aspiration cytology provides a cost-effective means for their evaluation as it is a very simple and effective. This procedure has avoided unnecessary surgical interventions by differentiating benign from malignant lesions. The sensitivity and specificity of aspiration cytology ranges from 90-100%.3, 4
Salivary gland lesions are known for their diversity and the heterogenecity of the morphological features and thereby many challenges are thrown to the pathologist in the process of final diagnosis. The important aspect is the differentiation of benign from malignant one.5, 6
FNAC has many diagnostic challenge because of the presence of histological features like basaloid pattern of the cells, cystic change, oncocytic and squamous metaplasia. 7 Subclassification of the lesion into benign, suspicious of malignancy or definitive malignancy was done in various studies thus stratifying the risk of malignancy.3 The risk varies from study to study ranging from 6 to 100% and lacks a consensus approach.8
Salivary gland reporting system lacks terminology and various systems have been in use from two tiered to six tiered system. The “Milan System for Reporting Salivary Gland Cytopathology” (MSRSGC), a tiered international classification scheme was proposed by the American Society of Cytopathology and International Academy of Cytology recently. This system (Table 1) provides a guide for clinical management depending on the risk of malignancy (ROM).9, 10
Table 1
The milan system for reporting salivary gland cytopathology (MSRSGC): Implied risk of malignancy and recommended clinical management
The current study was done to diagnose and classify the salivary gland lesions by the recent Milan system for assessment of the risk of malignancy.
Materials and Methods
All the cases referred to the department of Pathology from the Department of Surgery, ENT and Dental Surgery for evaluation of salivary gland lesions were included in the study. Clinical data and radiological assessment was done in all these cases. Fine needle aspiration was done. The slides were stained with H and E, PAP stain was used in cases where required. All the cases were reported by a single pathologist to avoid reporting bias and stratified into various categories according to MSRSGC.
Category 1: Non-diagnostic (ND)
Category 2: Non-neoplastic (NN)
Category 3: Atypia of undetermined significance (AUS)
Category 4a: Neoplasm: Benign (NB)
Category 4b: Neoplasm: Salivary gland neoplasm of uncertain malignant potential (SUMP)
Category 5: Suspicious of malignancy (SM)
Category 6: Malignant (M).
Only 105 cases came for follow up, for which histopathological examination was done. Risk of malignancy was thus calculated depending upon the histopathological features.
Results
In our study we had male predominance and most of the cases were seen in the age group of 21-40years.
Table 2
Distribution of cases according to age, sex, and site of involvement Sex distribution of the lesions
|
Sex |
No. of cases |
% |
|
Males |
118 |
51.5 |
|
Females |
107 |
48.5 |
|
Total |
225 |
100 |
Table 3
Age distribution of the lesions
|
Age group |
No. of cases |
% |
|
0-20 |
31 |
13.6 |
|
21-40 |
104 |
46.1 |
|
41-60 |
61 |
27 |
|
61-80 |
22 |
10.2 |
|
>81 |
7 |
3 |
|
Total |
100 |
|
Patients had presented with lesions in all the major and minor salivary glands-parotid, submandibular and sublingual. Majority of the cases were seen in the parotid gland.(57.7%).
Table 4
Site distribution of the lesions
|
Site |
No. of cases |
% |
|
Parotid |
130 |
57.7 |
|
Submandibular |
61 |
27.3 |
|
Sublingual |
34 |
15 |
|
Total |
100 |
|
Table 5
Age distribution of the lesions
|
Age group |
No. of cases |
% |
|
0-20 |
3 |
3.61 |
|
20-40 |
22 |
26.50 |
|
40-60 |
39 |
46.98 |
|
60-80 |
19 |
22.89 |
Cytological evaluation was done according to the Milan system as shown in Table 6.
Table 6
Histological follow-up of Milan system diagnostic categories
Discussion
FNAC is a safe, accurate, and cost-effective method for evaluation of salivary gland swelling and can help in management of the patient by avoiding unnecessary surgery in cases where there no malignancy as is assessed by the risk of malignany given by Milan system of scoring.11, 12, 13
The patient management is made easy by MSRSGC, a new system used for reporting salivary gland lesions with risk stratification. As discussed previously it is a evidence based six tiered system, providing risk of malignancy which is very useful for the treatment of the patients.11, 12, 13 The six categories as per this system are Non diagnostic(ND), Non neoplastic(N), Atypia of undetermined malignancy(AUS), Neoplasm-Benign (NB),Neoplasm-Suspicious of malignant potential(SUMP), Suspicious of malignancy(SM), and Malignant. Risk of malignancy(ROM) as given by this system is as follows: 25%, 10%, 20%, 5%, 35%, 60%, and 90% for each category.9 In our study after categorising the various lesions, we have assessed the risk of malignancy. ROM for the various categories is as follows: 25% for category I-Non diagnostic, 5%, for category II-Non neoplastic, 25% for category III-Atypia of undetermined significance,2.8% for category IV a – Neoplasm: Benign, 50%-IV b- Neoplasm:Salivary gland neoplasm of uncertain malignant potential, 100% for category V- Suspicious of malignancy and lastly 86.8% for category VI- Malignant. These results are comparable to those given in the Milan system.
We now discuss each category in detail with reference to the cytological and morphological features.
In the Category 1, in view of insufficient material for diagnosis, they are non-diagnostic so cannot give an informative interpretation. There were 6 cases (3.3%) in our study belonging to this category(ND). Histopathological follow-up revealed 4 cases to be chronic sialadenitis. 1 case was Pleomorphic adenoma, which in view of secondary changes, yielded an insufficient aspirate on fine needle aspiration.1 case was diagnosed as Adenocarcinoma with marked cystic change on histology that lead to insufficient aspiration on cytology.
Now we shall discuss the Category 2, non neoplastic. Only 40(44%) out of 90 cases came for follow up. Most of the cases have good cytomorphological co relation except for 1 case. This case was actually diagnosed as acute sialadenitis,but on histopathological examination, it was diagnosed as carcinoma-ex pleomorphic adenoma, the areas of necrosis seen in histopathology were actually mis interpreted as inflammatory debris and diagnosed as acute sialadenitis in cytology.
Under the next category, Atypia of undetermined significance, all the 4 cases came for follow up(100%). This category is a grey zone as malignancy cannot be ruled out. 3 cases were pleomorphic adenoma with mild atypia on histopathology. These atypicals cells were the reason for diagnosing as AUS on cytology. One case was Adenoid cystic carcinoma, the cells which seen as dispersed cells with atypia are the cells of adenoid cystic carcinoma with a different pattern(solid) mis diagnosed as atypia in cytology.
The 4th category has 4a and 4b.35 cases out of 72 have come for follow up. The most common benign lesion was Pleomorphic adenoma the maximum co relation was seen in this category. Only 1 case which was diagnosed as pleomorphic adenoma turned out to be carcinoma adenoid cystic carcinoma. The various patterns i.e. solid, trabecular and cribriform pattern were misinterpretated as epithelial and mypepithelial componnets in cytology and was underdiagnosed as Neoplasm Benign, possibility of Pleomorphic adenoma.
In cases where cytology is not able to differentiate between benign and malignancy we label it as suspicious of malignant potential.2 out 4 cases (50%) came for follow up. 1 case was non neoplastic on histology. The other was malignant, adenocarcinoma. Thus one case was over diagnosed as suspicious of nmalignacy in view of marked atypia which was actullay due to acute inflammatory process.
The 5th category, suspicious for malignancy is a entity for cases where the features are suggestive. All the 3 cases came for follow up were diagnosed as Adenoid cystic carcinoma giving rise to 100% efficacy between cytology and histopathology.
The last category included malignant. Here the features are very much diagnostic. 15 cases came for follow up. 13 cases were malignant on histopathology with ROM being 86.6%.1 case was pleomorphic adenoma which was signed out as malignant in cytology and other case was sialadenitis with severe atypia which again was diagnosed as malignant in cytology.
As we have limited studies in this field of cytology we would conclude that further research has to be done. The other limitation of our study is sample size.
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