Salivary Gland CytologyEdit
Salivary Gland Cytology is the cytological study of cells collected from lesions in the salivary glands, most often through minimally invasive sampling with a fine needle. The goal is to provide a rapid, cost-effective preoperative assessment that helps distinguish benign from malignant processes, identify cystic versus solid lesions, and guide subsequent management. The major salivary glands—the parotid, submandibular, and sublingual glands—are the common sources of aspirates, though sampled material may also come from minor salivary glands scattered throughout the oral mucosa. In routine practice, cytology serves as a triage tool that can spare patients unnecessary surgery when lesions are benign or indolent, while directing more definitive intervention when malignancy is suspected.
Cytology relies on the examination of individual cells and small clusters rather than intact tissue architecture. Because salivary gland tumors are diverse, a disciplined approach combines careful sampling, on-site adequacy assessment, and standardized reporting to achieve reliable diagnostic categories. Modern practice often couples traditional smear preparation with ancillary techniques such as cell blocks, immunocytochemistry, and, when indicated, molecular testing, to improve diagnostic specificity and provide actionable information for treatment planning. For imaging-guided sampling, ultrasonography is frequently employed to improve yield, especially for deep lobe or small lesions, and to avoid nearby structures such as nerves.
Overview and techniques
A typical diagnostic workflow begins with patient history and imaging, followed by sampling with fine-needle aspiration (Fine-needle aspiration). On-site evaluation may determine whether the specimen is sufficient for diagnosis, a process known as rapid on-site evaluation. If the sample is nondiagnostic or limited, repeat sampling or alternative approaches such as core needle biopsy (Core needle biopsy) may be considered, recognizing trade-offs between diagnostic yield and invasiveness.
Cell blocks, where cells are embedded in a paraffin block to resemble miniature histology sections, can be prepared from aspirates to allow additional staining and, when necessary, molecular testing. Immunocytochemistry (Immunocytochemistry) and targeted molecular assays can help characterize neoplasms that have overlapping cytologic features, such as distinguishing certain basaloid tumors or identifying myoepithelial differentiation. The combination of cytomorphology with ancillary studies is particularly valuable for distinguishing common entities such as pleomorphic adenoma, Warthin tumor, mucoepidermoid carcinoma, and adenoid cystic carcinoma.
Key cytology categories used in salivary gland evaluation are informed by standardized reporting systems. The Milan System for Reporting Salivary Gland Cytopathology (Milan System for Reporting Salivary Gland Cytopathology) provides a structured framework with categories ranging from nondiagnostic to malignant, along with estimated risk of malignancy to guide clinical decisions. This approach aims to reduce uncertainty and standardize communication among clinicians, radiologists, and pathologists.
Common benign and malignant entities encountered on cytology include:
- Pleomorphic adenoma, the most frequent benign salivary gland neoplasm, which characteristically shows a mix of epithelial and myoepithelial cells with a chondromyxoid stromal background.
- Warthin tumor (papillary cystadenoma lymphomatosum), often presenting with oncocytic epithelial cells and a prominent lymphoid stroma.
- Mucoepidermoid carcinoma, which displays a combination of mucin-producing cells, squamous (epidermoid) cells, and intermediate-type cells.
- Adenoid cystic carcinoma, notable for basaloid cells with cribriform or tubular architectural patterns and perineural invasion on histology; cytology can be challenging due to overlapping features with other basaloid lesions.
- Other malignant salivary gland neoplasms, including salivary duct carcinoma, epithelial-myoepithelial carcinoma, and various high-grade sarcomas or metastatic deposits in select cases.
Diagnostic categories and interpretation
Cytology reports commonly address cellular adequacy, the presence of neoplastic versus non-neoplastic processes, and the likelihood of malignancy. The use of the MSRSGC helps categorize specimens into clinically meaningful groups, such as nondiagnostic, benign, neoplasm of uncertain malignant potential, suspicious for malignancy, and malignant. Each category is linked to a corresponding risk of malignancy and recommended clinical action, aiding multidisciplinary decision-making.
Interpreting salivary gland cytology requires awareness of characteristic pitfalls. For example, pleomorphic adenoma can be mistaken for other basaloid neoplasms if the stromal component is underrepresented; mucoepidermoid carcinoma may be confused with benign mucous or metaplastic changes in inflammatory glands; and cystic lesions can yield limited cellular material, reducing diagnostic confidence. In such cases, integrating imaging features, clinical history, and ancillary studies improves accuracy. When necessary, a repeat FNA or a core biopsy may be pursued to obtain more definitive tissue.
Indications, limitations, and controversies
Salivary gland cytology excels as a minimally invasive, cost-conscious modality that can spare patients from unnecessary surgery and help tailor surgical planning, particularly when emotions surrounding facial nerve preservation or cosmetic outcomes are involved. It is particularly valuable in the workup of parotid and submandibular masses, known to harbor a mix of benign and malignant lesions. However, limitations include sampling error, especially in heterogeneous tumors or deeply located glands; overlap in cytomorphology between different tumor types; and variable specimen quality. In cystic or heavily inflammatory lesions, cytology may yield nondiagnostic or indeterminate results, necessitating additional sampling or a complementary diagnostic approach.
The ongoing debate in the field centers on the optimal balance between less invasive cytology and the need for more definitive histology. Some clinicians favor core needle biopsy in select cases where there is high suspicion for unusual neoplasms or when cytology is inconclusive, while others emphasize preserving nerves and reducing invasiveness by relying on repeat FNAs or open biopsy only when clearly indicated. There is also discussion about the role of comprehensive molecular profiling in routine salivary gland cytology, which can refine classification in ambiguous cases but raises considerations of cost, accessibility, and the clinical impact of such data on management decisions. Nonetheless, standardized reporting systems and careful integration with imaging and clinical context have improved consistency across centers and reduced rate of misinterpretation.
Clinical workflow and integration
In practice, salivary gland cytology sits at the intersection of radiology, pathology, and surgery. Ultrasound-guided sampling enhances yield for small or deep lesions and helps minimize complications. Adequate communication between the cytopathologist and the surgeon or clinician is essential, particularly when considering facial nerve preservation and reconstructive goals. When cytology indicates a benign neoplasm such as pleomorphic adenoma or Warthin tumor, conservative surgical planning may be appropriate. If cytology raises concern for malignancy, more definitive diagnostic steps and wider surgical planning, possibly including neck assessment for metastasis, become priorities.
Clinicians also weigh patient-specific factors such as age, overall health, and personal preferences. The integration of cytology with imaging findings—such as ultrasound characteristics or cross-sectional imaging—contributes to a comprehensive assessment that guides whether to observe, biopsy further, or proceed to surgery.