For salivary gland FNAs, it is currently recommended to use the “Milan System,” which includes 6 diagnostic categories:
Category 1: Non-Diagnostic
Risk of Malignancy: 25%
Clinical Management: Clinical and radiologic correlation/repeat FNA
– Salivary gland parenchyma (Non-diagnostic, Milan category 1) (see comment)
– Predominantly blood (Non-diagnostic, Milan category 1)(see comment)
COMMENT: The aspirate smears and cell block show ***. The clinical and radiographic impression of a salivary gland mass is noted. There are no cytologic findings to explain the impression of a mass. Clinical and radiographic correlation is recommended with suggested consideration for repeat biopsy if clinical concern persists.
Category 2: Non-Neoplastic
Risk of Malignancy: 10%
Clinical Management: Clinical and radiologic correlation
– Fibrinopurulent debris, compatible with abscess (Non-neoplastic, Milan category 2) (see comment)
COMMENT: The aspirate smears show abundant neutrophils, fibrin, and necrotic debris, consistent with sampling of an abscess. Clinical and radiographic correlation, as well as correlation with the pending microbiologic studies, is recommended.
– Reactive lymphoid hyperplasia (Non-neoplastic, Milan category 2)
COMMENT: The aspirate smears and cell block show a heterogenous mixture of small and large lymphocytes with a predominance of small lymphocytes. Rare tingible body macrophages are seen. There is no evidence of granulomatous inflammation or epithelial malignancy. In addition, no Reed-Sternberg cells are identified. The findings support reactive lymphoid hyperplasia. If there is persistence or progression of the adenopathy, repeat biopsy may be considered, if clinically indicated.
– Benign salivary gland parenchyma, compatible with sialadenosis (Non-neoplastic, Milan category 2) (see comment)
COMMENT: The aspirate smears and cell block show benign salivary gland elements including ducts and acini. The clinical and radiographic impression of bilateral salivary gland enlargement without any discrete lesion is noted. Together, the clinicopathologic findings are compatible with sialadenosis. Close clinical and radiographic correlation is recommended.
Category 3: Atypia of Undetermined Significance (AUS)
Risk of Malignancy: 20%
Clinical Management: Repeat FNA or Surgery
– Oncocytic lesion (Atypia of undetermined significance, Milan Category 3) (see comment)
COMMENT: The aspirate smears are moderately cellular and show clusters of bland cells with ovoid nuclei and abundant granular cytoplasm, consistent with oncocytes. No significant lymphoid population is seen in the background. The cell block shows nests and trabeculae of oncocytic cells. There is no significant cytologic atypia or necrosis. These features are consistent with an onocyctic lesion and the differential diagnosis includes oncocytic metaplasia/hyperplasia, oncocytoma, and Warthin’s tumor. Clinical and radiologic correlation is suggested.
– Rare atypical cells (Atypia of undetermined significance, Milan Category 3) (see comment)
COMMENT: The aspirate smears are paucicellular and show predominantly blood. Only rare cells with mild to moderate cytologic atypia, including moderate nuclear size enlargement and moderately irregular nuclear contours, are noted. This these findings are of undetermined significance and are best categorized as “Atypia of Undetermined Significance.” Clinical and radiographic correlation is recommended.
– Mucus only (Atypia of undetermined significance, Milan Category 3) (see comment)
COMMENT: The aspirate smears are hypocellular and show exclusively extracellular mucin. The differential diagnosis for a mucin-containing cyst includes a mucocele, mucus retention cyst, and low-grade mucoepidermoid carcinoma. Clinical and radiographic correlation is recommended with possible consideration for repeat aspiration of any remaining mass, is recommended.
Category 4: Neoplasm
Neoplasm: Benign
Risk of Malignancy: <5%
Clinical Management: Surgery or clinical follow-up
– Pleomorphic adenoma (Neoplasm, Milan category 4) (see comment)
COMMENT: The aspirate smears are abundantly cellular and show fragments of fibrillar metachromatic stroma with admixed cytologically bland myoepithelial and epithelial cells. Clusters of benign salivary gland acini are also identified. These findings are diagnostic of a pleomorphic adenoma (benign mixed tumor). Clinical and radiographic correlation is recommended.
– Warthin’s tumor (Neoplasm, Milan category 4) (see comment)
COMMENT: The aspirate smears and cell block are moderately cellular and show clusters of cytologically bland epithelial cells with eosinophilic, granular cytoplasm, and distinct cell borders. There is a background of lymphoid tissue. There is also amorphous debris associated with histiocytes, consistent with a cystic component. Benign salivary gland elements are also present. These findings are compatible with a Warthin tumor. Clinical and radiographic correlation is recommended.
Neoplasm: Salivary Gland Neoplasm of Uncertain Malignant Potential (SUMP)
Risk of Malignancy: 35%
Clinical Management: Surgery
– Basaloid salivary gland neoplasm (Neoplasm, Milan category 4) (see comment)
COMMENT: The aspirate smears are abundantly cellular and show groups of small, bland basaloid cells with mildly enlarged, ovoid nuclei surrounding well-defined, metachromatic hyaline globules of stroma. The core biopsy shows fragments of bland basaloid cells associated with hyalinized fibrillary stroma with focal myxoid change and admixed myoepithelial cells. Scattered tubules are present. No high-grade atypia, necrosis, or mitotic activity is seen. We favor these findings to represent a benign salivary gland neoplasm, most likely cellular pleomorphic adenoma; however, adenoid cystic carcinoma cannot be entirely excluded based on the morphologic findings. Clinical and radiographic correlation is recommended.
Category 5: Suspicious for Malignancy
Risk of Malignancy: 60%
Clinical Management: Surgery
– Low-grade salivary gland neoplasm, suspicious for mucoepidermoid carcinoma (Suspicious for malignancy, Milan category 5) (see comment)
COMMENT: The aspirate smears and cell block are abundantly cellular and show cytologically bland epithelial cells arranged in small clusters. The epithelial cells have abundant eosinophilic granular cytoplasm with prominent intracytoplasmic vacuolization suggestive of cytoplasmic mucin. The nuclei are moderately enlarged with regular nuclear borders and have variably prominent nucleoli. There is no evidence of high-grade cytologic atypia, necrosis, or increased mitotic activity. PASD shows abundant intracytoplasmic mucin within the neoplastic cells. The cytologic features are most consistent with a primary salivary gland neoplasm with features highly suspicious for mucoepidermoid carcinoma. However, definitive classification of this salivary gland neoplasm is best deferred to the anticipated excision specimen.
– Suspicious for squamous cell carcinoma (Suspicious for malignancy, Milan category 5) (see comment)
COMMENT: The aspirate smears show keratinaceous debris with numerous anucleate keratinocytes and necrosis. Scattered keratinocytes are identified with moderate nuclear atypia. Dyskeratotic cells are also identified. Together, these findings are suspicious for a carcinoma with squamous differentiation, including possibly a metastatic keratinizing squamous cell carcinoma. Clinical and radiographic correlation is recommended.
Category 6: Malignant
Risk of Malignancy: 90%
Clinical Management: Surgery
– Adenoid cystic carcinoma (Malignant, Milan category 6)
COMMENT: The aspirate smears are abundantly cellular and show a basaloid salivary gland neoplasm with numerous hyaline stromal balls. The cell block shows similar findings. These findings are most consistent with adenoid cystic carcinoma. Clinical and radiographic correlation is recommended.
– High-grade carcinoma (Malignant, Milan category 6) (see comment)
COMMENT: The aspirate smears are abundantly cellular and show a proliferation of cohesive cells with severe nuclear pleomorphism and moderate amounts of cytoplasm. No gland formation or intracellular mucin is identified. No stroma production by tumor cells is seen. These findings are diagnostic of high-grade carcinoma. The differential diagnosis includes salivary duct carcinoma and poorly-differentiated squamous cell carcinoma, among other possibilities. Final pathologic classification is deferred to the anticpated resection specimen. Clinical and radiographic correlation is recommended.
Last updated: September 10, 2019