Parotid tumors constitute a heterogeneous group of salivary gland neoplasms with marked variation in histology and biological behavior. The fifth edition of the World Health Organization classification of head and neck tumors recognizes an expanding spectrum of benign and malignant salivary entities, including newly characterized tumor types. This diversity complicates direct comparison among historical series and reinforces the importance of contemporary pathological classification. The facial nerve traverses the parotid gland and is a defining anatomical consideration in treatment. A painless, slowly enlarging parotid mass is a common presentation, whereas pain, facial nerve dysfunction, fixation, skin involvement, rapid growth and cervical lymphadenopathy increase concern for malignancy. Preoperative evaluation combines clinical assessment, imaging and tissue sampling. Fine-needle aspiration (FNA) remains widely used; a meta-analysis of 70 studies found moderate sensitivity and high specificity for differentiating malignant from benign parotid lesions, while comparative evidence suggests core needle biopsy can reduce nondiagnostic sampling and improve diagnostic performance. Surgery is the mainstay for most operable parotid neoplasms. For benign tumors, the historical progression from enucleation toward formal parotidectomy has more recently been accompanied by renewed interest in extracapsular dissection and partial superficial parotidectomy for carefully selected lesions. For malignant tumors, the goals are complete excision with negative margins, appropriate facial nerve management, selective or comprehensive treatment of the neck when indicated, and risk-adapted postoperative radiotherapy. This review aims to synthesize evidence concerning (1) clinicopathological patterns, (2) preoperative diagnosis, (3) surgical strategies, (4) facial nerve and other postoperative outcomes, and (5) oncological considerations in malignant parotid tumors.

Reporting framework and protocol The review is intended to be reported according to PRISMA 2020. Prospective protocol registration (for example, PROSPERO where eligible) should be completed before the definitive search if the review has not yet commenced. Any protocol deviations should be documented in the final manuscript. Eligibility criteria Population: patients with primary benign or malignant parotid tumors. Intervention/exposure: diagnostic assessment and/or surgical management of the parotid primary, with or without neck management or adjuvant treatment. Outcomes: histopathological distribution, diagnostic performance, extent of surgery, facial nerve dysfunction, Frey syndrome, salivary complications, recurrence, nodal disease and survival. Eligible designs should include systematic reviews/meta-analyses, randomized or nonrandomized comparative studies, and observational cohorts with extractable parotid-specific outcomes. Case reports, very small uncontrolled series, non-parotid salivary tumors without separable data, and non-human studies should be excluded from the primary synthesis. Information sources and search strategy Planned databases: PubMed/MEDLINE, Embase, Scopus, Web of Science and Cochrane Library from inception to the final search date. A draft PubMed strategy is: ("parotid neoplasms"[MeSH Terms] OR "parotid tumor*" OR "parotid tumour*" OR "parotid neoplasm*") AND ("parotidectomy" OR "extracapsular dissection" OR "superficial parotidectomy" OR "facial nerve" OR "histopathology" OR "outcome*" OR "recurrence"). [FINAL SUBMISSION: adapt syntax to each database and report the complete strategies in a supplement.] Study selection and data extraction [TO COMPLETE BEFORE SUBMISSION] Two reviewers should independently screen titles/abstracts and full texts, with disagreements resolved by consensus or a third reviewer. Extract study design, country, sample size, age, sex, benign/malignant distribution, histology, diagnostic modality, operation, facial nerve outcomes, complications, recurrence, follow-up and oncological outcomes. Risk of bias and certainty [TO COMPLETE BEFORE SUBMISSION] Use a design-appropriate tool: ROBINS-I or Newcastle-Ottawa Scale for observational comparative studies, RoB 2 for randomized trials, and AMSTAR 2 when formally evaluating included systematic reviews. If a de novo meta-analysis is performed, consider GRADE for key outcomes. Synthesis and statistical analysis Because the current draft synthesizes heterogeneous published evidence at different levels (cohorts, meta-analyses and guidelines), no new pooled estimate has been calculated. Published pooled estimates are reproduced with attribution. If the final systematic search identifies sufficiently homogeneous primary studies, a random-effects meta-analysis may be performed for prespecified outcomes. Dichotomous comparative outcomes should be expressed as risk ratios or odds ratios with 95% confidence intervals; continuous outcomes as mean differences or standardized mean differences. Statistical heterogeneity should be quantified using I² and tau², with subgroup/sensitivity analyses planned a priori.

Study selection [PRISMA PLACEHOLDER - MUST BE COMPLETED FROM THE FINAL DATABASE SEARCH] Records identified: [ ]; duplicates removed: [ ]; titles/abstracts screened: [ ]; full texts assessed: [ ]; studies included: [ ]. Do not submit a numerical PRISMA diagram until these values are generated from the actual search and screening process. Clinicopathological spectrum The published literature consistently demonstrates predominance of benign pathology in surgical parotid cohorts, although proportions vary by geography, referral pattern and inclusion criteria. A prospective Indian cohort of 59 patients reported 77.97% benign tumors and a benign-to-malignant ratio of 3.5:1; pleomorphic adenoma was the leading benign tumor and mucoepidermoid carcinoma the leading malignant tumor. A North Indian retrospective cohort of 102 operated patients similarly found pleomorphic adenoma to be the dominant benign neoplasm (76.5%) and mucoepidermoid carcinoma the most common malignant neoplasm (3.9% of the entire cohort). In a Turkish cohort of 170 parotidectomies, 85.3% were benign and 14.7% malignant; pleomorphic adenoma and Warthin tumor accounted for 39.4% and 32.9%, respectively. Preoperative diagnosis A systematic review and meta-analysis of parotid FNA included 70 eligible studies, with 63 studies (5,647 patients) contributing numerical outcomes. In the prospective subgroup, pooled sensitivity for malignancy was 0.882 (95% CI 0.509-0.982) and specificity was 0.995 (95% CI 0.960-0.999). The pooled probabilities of nondiagnostic and indeterminate cytology were 5.3% and 14.7%, respectively. A separate meta-analysis of six comparative studies (1,924 procedures) found that core needle biopsy produced fewer nondiagnostic results and higher sensitivity and specificity than FNA for detecting salivary malignancy, with hematoma reported in 0.3% of core biopsies. Surgical management of benign tumors A 2021 Bayesian network meta-analysis of 44 studies comprising 7,841 participants compared enucleation, extracapsular dissection (ECD), partial superficial parotidectomy (PSP), superficial parotidectomy (SP) and total parotidectomy (TP). Reported recurrence rates were 14.3%, 3.6%, 3.7%, 2.8% and 1.4%, respectively. The analysis found no statistically significant recurrence difference among ECD, PSP, SP and TP, while temporary facial weakness and Frey syndrome generally increased with greater extent of resection. A 2026 meta-analysis comparing ECD with PSP across 14 studies found ECD associated with shorter operating time, lower drainage volume, shorter hospital stay, and lower rates of Frey syndrome and temporary facial nerve injury, with no significant difference in recurrence or permanent facial nerve injury. Facial nerve outcomes and deep-lobe disease Facial nerve dysfunction remains one of the most clinically important complications of parotid surgery. In a retrospective study of 1,018 patients undergoing initial surgery for benign parotid tumors, postoperative facial palsy occurred in 19.5%; larger tumors and deep-lobe tumors were associated with higher risk, and all palsies in that cohort recovered within 24 months. A systematic review and meta-analysis of eight studies including 379 deep-lobe tumors reported a malignancy rate of 26.6% and significantly greater malignancy risk than superficial-lobe tumors (RR 1.25, 95% CI 1.01-1.56). Temporary postoperative facial weakness occurred in 32.5% of deep-lobe tumors versus 11.7% of superficial-lobe tumors. Other postoperative morbidity Frey syndrome is influenced by the extent of parotid resection and reconstructive strategy. A network meta-analysis including 3,830 patients found significant reductions in subjective Frey syndrome with temporoparietal fascia flap, acellular dermal matrix, free fat graft, sternocleidomastoid flap and SMAS flap compared with no interposition. In representative Indian cohorts, transient facial weakness was reported in approximately 22-23%, while permanent facial weakness varied between series and was concentrated among patients with malignant or more extensive disease. Malignant parotid tumors Management of malignant parotid tumors is driven by histological grade, T and N stage, facial nerve involvement, margins and other adverse pathological features. ESMO-EURACAN guidance identifies complete surgical excision with free margins as the foundation of treatment. The facial nerve should generally be preserved when it is not infiltrated or grossly encased; a preoperatively paralysed nerve due to tumor involvement may require resection with reconstruction/reanimation. Clinically node-positive salivary gland cancer warrants therapeutic neck dissection, while management of the cN0 neck is risk-adapted. ASCO guidance supports postoperative/elective neck irradiation in selected high-risk settings, including T3-T4 or high-grade malignancies. Prognostic evidence is histology-dependent. In a systematic review of parotid mucoepidermoid carcinoma, adverse survival associations were repeatedly observed for high histological grade, nodal disease, distant metastasis, intraparotid metastasis and increasing age. A 165-patient parotid cancer cohort also identified nodal positivity as a major adverse prognostic factor. Table 1: Representative clinicopathological cohorts Study Design / N Key clinicopathological findings Key outcomes Subhashraj et al. / prospective Indian cohort (2019) Prospective; N=59 Benign 77.97%; benign:malignant 3.5:1; PA most common benign; MEC most common malignant SP 69.49%; transient facial palsy 22.03%; permanent palsy 6.78% North India tertiary-centre cohort (2023/2024) Retrospective; N=102 Swelling 95.1%; PA 76.5%; Warthin 2.9%; MEC 3.9% Temporary facial weakness 23.28%; permanent facial weakness 5.0%; ear-lobule sensory impairment 35% Turkish tertiary-centre cohort (2020) Retrospective; N=170 Benign 85.3%; malignant 14.7%; PA 39.4%; Warthin 32.9% SP 78.2%; FNAC sensitivity 64.71%, specificity 100%, accuracy 94.92% Benign parotid facial palsy cohort (2021) Retrospective; N=1,018 PA 614; Warthin 234 Postoperative facial palsy 19.5%; higher with large/deep-lobe tumors; no permanent palsy in cohort Table 2: High-level evidence informing diagnosis and surgery Evidence source Studies / participants Principal findings Parotid FNA systematic review/meta-analysis (2016) 70 eligible; 63 quantitative; N=5,647 Prospective subgroup sensitivity 88.2%; specificity 99.5%; nondiagnostic 5.3%; indeterminate 14.7% CNB vs FNA meta-analysis (2020) 6 studies; 1,924 procedures CNB: fewer nondiagnostic results and higher sensitivity/specificity; hematoma 0.3% Benign surgery network meta-analysis (2021) 44 studies; N=7,841 Recurrence: enucleation 14.3%, ECD 3.6%, PSP 3.7%, SP 2.8%, TP 1.4%; greater resection associated with more temporary weakness/Frey syndrome Deep-lobe systematic review/meta-analysis (2022) 8 studies; 379 deep-lobe tumors Malignancy 26.6%; RR vs superficial lobe 1.25 (95% CI 1.01-1.56); temporary weakness 32.5% vs 11.7% ECD vs PSP meta-analysis (2026) 14 studies ECD: shorter surgery/hospital stay, less drainage, less temporary FN injury and Frey syndrome; no significant recurrence/permanent FN injury difference Permanent palsy/recurrence network meta-analysis (2026) 23 studies; N=4,674 Mean recurrence 2.9%; mean permanent palsy 3.0%; no significant recurrence difference for ECD or TP vs partial parotidectomy in random-effects network model Table 3: Practical evidence synthesis by clinical domain Domain Evidence-based synthesis Clinical implication Histology Benign tumors predominate in most surgical cohorts; PA is usually the commonest benign tumor. Final histopathology remains essential; modern WHO terminology should be used. Preoperative tissue diagnosis FNA has high specificity but variable sensitivity; CNB may improve diagnostic yield when malignancy is suspected. Choose sampling strategy according to clinical/imaging suspicion and local expertise. Benign superficial tumors ECD/partial procedures show low recurrence in selected tumors with lower temporary facial morbidity in several meta-analyses. Extent of surgery should be individualized; avoid simple enucleation. Deep-lobe tumors Higher malignancy rate and temporary facial weakness than superficial-lobe tumors. Cross-sectional imaging and careful facial-nerve counselling/planning are particularly important. Malignant tumors Margin status, grade, nodal disease and nerve involvement influence management and prognosis. Multidisciplinary, risk-adapted surgery, neck management and radiotherapy are required. Frey syndrome Interposition/reconstructive techniques can reduce clinical Frey syndrome. Reconstruction can be considered according to defect, risk and expertise.

This evidence synthesis demonstrates three recurring themes in parotid tumor management: marked histopathological heterogeneity, the need to balance oncological adequacy against facial nerve morbidity, and the importance of tailoring treatment to tumor biology and anatomical extent. Although benign lesions dominate most surgical cohorts, the relative proportions of pleomorphic adenoma, Warthin tumor and malignant histologies differ substantially across institutions and regions. Such variation likely reflects referral patterns, demographic differences, smoking prevalence, diagnostic classification and selection of operated rather than all diagnosed lesions. Pleomorphic adenoma remains the principal benign tumor in many series, including Indian cohorts. The historical concern with recurrence after inadequate surgery is reflected in the substantially higher recurrence rate reported for enucleation in network meta-analysis. Contemporary evidence, however, does not support a simple assumption that more extensive surgery is always superior for every benign lesion. ECD and partial superficial procedures can achieve low recurrence in appropriately selected mobile, superficial tumors while reducing temporary facial nerve dysfunction and Frey syndrome. Selection is crucial: results from limited surgery should not be generalized to large, recurrent, deep-lobe, fixed or suspicious tumors. The diagnostic literature supports a complementary rather than competitive view of imaging and tissue sampling. FNA is minimally invasive and highly specific when adequate, but nondiagnostic and indeterminate samples remain clinically relevant. Core needle biopsy preserves tissue architecture and may improve tumor typing and malignancy detection, particularly when imaging or clinical findings are suspicious. Nevertheless, procedure selection depends on operator expertise, lesion characteristics and institutional pathways. Facial nerve outcome is a key quality measure in parotid surgery. The higher temporary weakness observed with deep-lobe tumors is anatomically plausible because access often requires greater nerve dissection and manipulation. Tumor size, deep-lobe location, revision surgery and malignant behavior can confound comparisons of facial nerve outcomes between operative techniques. Consequently, observational comparisons should not be interpreted as proof that a particular procedure itself causes the entire observed difference in nerve dysfunction. For malignant disease, the evidence base is constrained by rarity and histological diversity. Current ESMO-EURACAN and ASCO recommendations emphasize complete surgical excision when feasible, preservation of an uninvolved facial nerve, therapeutic management of clinically involved nodes, risk-adapted treatment of the cN0 neck and postoperative radiotherapy for appropriate adverse-risk features. Histological grade and nodal disease repeatedly emerge as important prognostic variables, but the prognostic weight of individual factors varies by histological subtype. The review also highlights methodological limitations in the literature. Most surgical evidence is retrospective, terminology for limited parotidectomy is inconsistent, indications differ among centres, and follow-up is often insufficient for tumors capable of late recurrence. Meta-analyses therefore inherit selection bias and heterogeneity from their component studies. Future studies should use standardized operative definitions, contemporary WHO classification, validated facial nerve grading, clearly defined temporary/permanent dysfunction, and sufficiently long oncological follow-up. Limitations of this review draft This document is a manuscript-development draft based on a focused, verifiable literature search rather than a completed de novo PRISMA systematic review. It intentionally does not invent database record counts, duplicate removal, screening decisions or risk-of-bias ratings. Before journal submission, the authors must complete those steps and update the Results, PRISMA diagram, evidence tables and, if appropriate, quantitative synthesis. The current numerical results are published estimates from cited studies and meta-analyses and should not be interpreted as a newly pooled dataset.

Parotid tumors encompass a broad clinicopathological spectrum in which benign neoplasms predominate but malignant disease requires careful preoperative recognition and risk-adapted treatment. Pleomorphic adenoma remains the leading benign histology in many cohorts. FNA is highly specific but may be nondiagnostic or indeterminate, while core biopsy can improve diagnostic yield in selected patients. For appropriately selected benign superficial tumors, contemporary evidence supports limited parotid surgery as an oncologically reasonable strategy with potential reductions in temporary facial nerve morbidity; simple enucleation has a less favorable recurrence profile. Deep-lobe and malignant tumors carry greater complexity and require individualized multidisciplinary planning. Standardized prospective reporting and long-term follow-up are needed to strengthen comparative evidence.

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