From the Guidelines
Salivary gland biopsy, either fine needle aspiration biopsy (FNAB) or core needle biopsy (CNB), is strongly recommended to support the distinction of salivary gland cancers from nonmalignant salivary lesions. This approach is based on high-quality evidence from the American Society of Clinical Oncology (ASCO) guideline published in 2021 1. The guideline emphasizes the importance of tissue biopsy in the management of salivary gland malignancy, highlighting its role in distinguishing between malignant and nonmalignant lesions.
When considering the diagnostic approach, it's essential to note that fine-needle aspiration biopsy (FNA) is often the preferred initial method due to its minimally invasive nature and high diagnostic accuracy. The procedure involves using a 22-25 gauge needle to extract cellular material from the suspicious mass, which is then prepared for cytological examination. This can be performed in an outpatient setting under local anesthesia, frequently with ultrasound guidance to enhance accuracy. For parotid tumors, FNA has demonstrated a sensitivity of approximately 70-90% and a specificity of 90-95% 1.
Key points to consider in the diagnostic process include:
- The use of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) for categorizing cytopathology results, which helps in providing more nuanced information for decision-making 1.
- The potential need for core needle biopsy or incisional biopsy in cases where FNA results are inconclusive or when more tissue is required for a definitive diagnosis.
- The avoidance of open surgical biopsy as the initial diagnostic procedure due to associated risks such as tumor seeding, facial nerve injury, and potential complications like fistula formation.
The biopsy results are crucial for determining the nature of the tumor (benign vs. malignant) and guiding appropriate treatment planning, which may include surgical excision, radiation therapy, or observation depending on the tumor type. It's also important for patients to be informed about the potential complications of salivary gland biopsies, including bleeding, infection, temporary pain, and rarely, nerve damage. The recommendation for salivary gland biopsy is based on the most recent and highest quality evidence available, prioritizing morbidity, mortality, and quality of life as outcomes 1.
From the Research
Role of Salivary Gland Biopsy in Diagnosing Salivary Gland Tumors
- Salivary gland biopsy plays a crucial role in diagnosing salivary gland tumors, with fine-needle aspiration biopsy (FNAB) being a widely used method 2, 3, 4.
- The accuracy of FNAB in diagnosing salivary gland tumors varies, with sensitivity ranging from 53.3% to 76.9% and specificity ranging from 95.4% to 95.8% 2, 3, 4.
- FNAB is useful in diagnosing benign tumors, but its sensitivity is lower for malignant tumors, which can lead to false negatives 2, 3.
- The use of ultrasound-guided fine-needle aspiration biopsy (US-FNAB) and ultrasound-guided core needle biopsy (US-guided CNB) can improve the diagnostic accuracy of salivary gland biopsies 5.
- Intra-operative frozen sections (IOFSs) can also be used as an additional diagnostic method to improve the accuracy of salivary gland biopsies 5.
- A pattern-based approach to the evaluation of small salivary biopsies, including consideration of clinical and radiographic information, systematic assessment of histologic patterns, and judicious use of immunohistochemistry and molecular studies, can facilitate the most complete and useful classification possible 6.
- The major drawbacks of FNAB include a lower sensitivity than specificity and a relatively high rate of non-diagnostic results 4.