Reclassification of Salivary Gland Aspirates Based on "The Milan System for Reporting Salivary Gland Cytology": A Five-Year Retrospective Study

Abstract

Introduction: The Milan System for reporting salivary gland cytopathology helps standardize reporting systems across institutions, improve communication between clinicians and pathologists and guide the clinical management of patients.

Aims: This study was undertaken to evaluate the utility of the Milan system classification in cytology reporting.

Settings and design: The present study is a retrospective study conducted over a period of five years in tertiary care centre.

Methods and materials: All the cases of salivary gland aspirates were reviewed and reclassified into six diagnostic categories according to the Milan system of reporting salivary gland cytology (MSRSGC). Cytological diagnosis was correlated with the histopathological diagnosis wherever available.

Results: A total of 258 cases were classified using the Milan system as non-diagnostic (20.9%), non-neoplastic (26.3%), atypia of undetermined significance (4.7%), neoplasm benign (37.5%), neoplasm of uncertain malignant potential (3.5%), suspicious for malignancy (0.4%), and malignancy (6.6%). Cytohistological discordance was noted among 8/76 cases (10.5%). The sensitivity and specificity of FNAC were 75% and 98.5%, respectively. The risk of malignancy was 14.2% for Category I, 9% for II, 50% for III, zero for IVA and IVB, and 83.3% for category VI.

Conclusions: The new classification system helps pathologists to standardize reporting leading to better clinical and surgical management.

Keywords: Milan system; risk of malignancy; salivary gland.

Figure 1

(a) Fine needle aspiration smear showing predominantly inflammatory cells with lack of epithelial component (Category I) (Papanicolaou 200×) (b) Follow-up histological examination showed low grade mucoepidermoid carcinoma (H and E 200×) (c) Aspirate showing benign salivary gland acini and variable mononuclear inflammatory cell infiltrate in the background. (Category II) (H and E 200×) (d) Follow-up histology revealed carcinoma ex pleomorphic adenoma with squamous cell carcinoma as the malignant

Figure 2

(a) Paucicellular fine needle aspiration smear showing acinar like-cluster of cells with bland nuclei and finely vacuolated cytoplasm (Category III) (MGG 200×) (b and c) Follow-up histological examination revealed acinic cell carcinoma comprising of acinar cells admixed with intercalated duct cells and microcsytic spaces (H and E 200 × and 100×)

Figure 3

(a) Fine needle aspiration smear of pleomorphic adenoma with characteristic fibrillary chondromyxoid stroma (Category IVA) (MGG 200×) (b and c) Histology showing classical pleomorphic adenoma (H and E 200×) (c) Aspirate of an oncocytic neoplasm showing cellular neoplasm with cohesive clusters of cells with central nuclei and oncocytic cytoplasm. (Category IVB) (Papanicolaou 200×) (d) Cluster of basaloid epithelial cells with crowding, hyperchromasia and scant cytoplasm, reported as basaloid ne

Figure 4

(a) Aspirate showing highly atypical cell cluster with moderate pleomorphism and nuclear hyperchromasia, reported as poorly differentiated carcinoma (Category VI) (H and E 400×) (b) Histology showing poorly differentiated adenocarcinoma (H and E 200×) (c) Aspirate of low grade mucoepidermoid carcinoma showing clusters of mucin secreting cells against a mucoid background (Category VI) (H and E 200×) (d) Follow-up histology of low grade mucoepidermoid carcinoma (H and E 200×)

Figure 5

(a) Aspirate reported as squamous cell carcinoma with necrosis (category VI) (Papanicolaou 200×) (b) Follow-up histology revealed Warthin's tumor (H and E 200×). In this case, the dirty background of cyst contents and oncocytic cells in Warthin's tumor was misinterpreted as atypical squamous cells in a background of necrosis. (c) Aspirate showing sheets of monomorphic population of uniform round cells (Category VI) (MGG 200×) (d) Histology reported as small round cell neoplasm (H and E 200×)