Update on Salivary Gland Fine-Needle Aspiration and the Milan System for Reporting Salivary Gland Cytopathology

FNA is established for diagnosing salivary gland lesions despite challenges due to tumor diversity and cytomorphologic overlap.
Reporting inconsistencies led to diagnostic confusion prior to 2015.
The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was developed to provide a standardized reporting framework.
MSRSGC includes 6 diagnostic categories with associated risks of malignancy and management recommendations.

Review current status of salivary gland FNA, core needle biopsies, ancillary studies, and the MSRSGC's role in clinical management.

The main goal of the MSRSGC is to enhance communication between cytopathologists and clinicians, improving reporting standards and patient management.
Endorsed by American Society of Clinical Oncology guidelines for salivary gland cancer (2021).

Majority occur in major glands, particularly the parotid, usually benign (e.g., pleomorphic adenoma, Warthin tumor).
Salivary malignancies account for 1%-5% of head and neck cancers.
Risk of malignancy (ROM) varies by anatomic location:
- 20%-25% in parotid
- 40%-50% in submandibular
- 50%-81% in sublingual and minor salivary glands.

Differentiating neoplastic from non-neoplastic lesions is critical for management and avoiding unnecessary surgeries.
Most salivary tumors require surgical excision; the surgery extent depends on diagnosis (e.g., facial nerve preservation for parotid tumors).
Benign tumors, especially Warthin tumors, may be monitored clinically.
Management of metastatic disease varies by primary site and tumor extent.

FNA is widely accepted as a first-line diagnostic test for salivary gland lesions: rapid, minimally invasive, and cost-effective.
FNA performance can vary significantly in sensitivity and specificity due to factors like:
- Operator experience
- Cytologic preparation quality
- Presence of cystic/necrotic components.
Average sensitivity ranges from 86%-100% and specificity from 90%-100% in distinguishing malignant from benign lesions.
Inadequate or non-diagnostic samples range from 0%-50% (mean 16.9%).
False-negative and false-positive rates are rare with salivary FNA.

High morphologic diversity in salivary gland tumors complicates diagnosis.
Difficult-to-interpret lesions include certain cellular neoplasms, cystic lesions, and lymphoid lesions.
Some benign and malignant tumors exhibit significant cytomorphologic overlap.

CNB provides a preserved tissue architecture specimen, serving as an alternative diagnostic tool.
Recommended when FNA is inadequate or non-diagnostic.
Reported sensitivity for CNB is 94%, with a specificity of 98%.
CNBs are generally utilized for minor salivary gland evaluations.

Using intraoperative frozen sections can help evaluate tumor invasion, influencing surgical decisions (e.g., nerve preservation).
High accuracy rates reported for identifying benign vs. neoplastic lesions (99% for neoplasms).

Standardizes terminology for clarity in communication among healthcare providers.
Enables comparison of data across institutions for quality improvement and research.
Facilitates medicolegal risk reduction concerning communication errors.

Ancillary studies are used for refining diagnoses within the indeterminate categories (SUMP, AUS).
They have enhanced the ability to classify salivary gland FNA results accurately.
Integration of molecular and immunohistochemistry techniques is evolving, improving diagnostic precision.

FNA and CNB play essential roles in preoperative evaluation of salivary gland lesions, with reforms improving diagnostic accuracy and patient management.
The MSRSGC serves as a crucial framework for enhancing communication and standardization in salivary gland cytopathology reporting.