Application of the Milan System for Reporting Salivary Gland Cytopathology: Experience of an academic institution in a tertiary academic medical center

A Retrospective Cytomorphologic Analysis of Salivary Gland Fine Needle Aspirates Classified as Salivary Gland Neoplasm of Uncertain Malignant Potential: A 6-year Institutional Experience

BACKGROUND

The Milan System for Reporting Salivary Gland Cytopathology is an effective reporting system for salivary gland fine needle aspirations with well-established risks of malignancy. Salivary gland neoplasm of uncertain malignant potential (SUMP) comprises a heterogenous group of lesions which have features that can be recognized as at least neoplastic but preclude further classification into benign or malignant. In this study, we reviewed the cytomorphologic features of salivary gland fine needle aspirations diagnosed as SUMP at our institution (over the past 6 years) and correlated those with the final diagnosis on surgical follow up.

DESIGN

A retrospective search was performed to identify cases classified as SUMP at our institution from January 2018 to February 2024. Cytology slides were reviewed, and cases were subclassified based on key cytomorphologic features into the following categories: (1) basaloid, (2) oncocytic, (3) with clear cell features and (4) mixed features (myoepithelial/oncocytoid/squamoid features). Histologic diagnosis was recorded if available.

RESULTS

A total of 36 cases of SUMP were identified; 31/36 had surgical follow up; final diagnosis included 22 benign lesions (2 non-neoplastic and 20 benign neoplasms), and nine malignant lesions. The overall risk of neoplasm and risk of malignancy were 93.5% and 29% respectively, with the oncocytic sub-category recording the highest ROM (42.8%). Mucoepidermoid carcinoma was the most common malignant diagnosis and pleomorphic adenoma the most common benign diagnoses.

CONCLUSIONS

Our study supports the subclassification of SUMP lesions based on key cytomorphologic features, thereby aiding in refining this ambiguous entity and providing a precise risk assessment.

Rapid on-site evaluation improves diagnostic performance of fine-needle aspiration cytology for salivary lesions: Comparison of data from two cancer centers in southern China

OBJECTIVES

To evaluate the diagnostic performance of Milan system for reporting salivary gland cytopathology (MSRSGC) in two southern China tertiary cancer centers and investigate the impact of rapid on-site evaluation (ROSE) on FNAC performance.

MATERIALS AND METHODS

Five hundred and forty-nine patients who underwent FNAC for salivary lesions with surgical follow-up from two centers were enrolled in this retrospective cohort study. All slides were recategorized using MSRSGC after consensus on diagnostic criteria for each category. The diagnostic performance of FNAC for salivary lesions was evaluated and compared and the impact of ROSE on FNAC performance was analyzed.

RESULTS

The distribution of cases per category based on the MSRSGC criteria in the whole series was as followed: ND 49 (8.9%), NN 76 (14.4%), BN 262 (47.7%), AUS 20 (3.6%), SUMP 43 (7.8%), SM 21 (3.8%), M 78 (14.2%). The SUMC series had significantly more ND distributions than JXCH did (16.2% vs. 0, p = .000). Risk of malignancy for each category in the total series was as followed: 42.9% for ND, 9.2% for NN, 3.8% for BN, 30.0% for AUS, 23.3% for SUMP, 81.0% for SM, and 94.9% for M. When ND and AUS/SUMP were excluded, the sensitivity, specificity, PPV, NPV, and accuracy were 84.0%, 97.1%, 89.9%, 95.1%, and 94.0%, respectively; sensitivity, specificity, PPV, NPV, and accuracy were comparable between the two centers.

CONCLUSIONS

FNAC using MSRSGC provides a good tool in preoperative evaluation for salivary lesions in southern China. ROSE improves its diagnostic performance by reducing the ratio of the ND category.

Interobserver Reliability of Milan and Modified Milan System for Reporting Salivary Gland Cytopathology: An Institutional Experience

Background

In 2018, the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was published, defining a diagnostic categorization scheme. However, this system of classification was criticized due to its suboptimal diagnostic accuracy and low interobserver reliability. For these reasons, the modified Milan system was recently proposed by a few authors claiming it to be more clinically reliable. The present study aimed to analyze the interobserver reliability of MSRSGC and modified MSRSGC.

Methods

A total of 100 salivary gland fine-needle aspirations were reviewed over a 1-year period and classified by two independent observers according to MSRSGC and modified MSRSGC. Interobserver reproducibility was estimated using observed agreement and chance-corrected agreement (Cohen's kappa).

Results

An overall chance corrected agreement of 0.37 (fair) was obtained for the original Milan system and 0.41 (moderate) for the modified one. In addition, subcategories of modified MSRSGC performed better than the MSRSGC in terms of interobserver reliability.

Conclusion

The present study suggests that modified MSRSGC should be accepted worldwide as the clinical relevance of any categorization scheme requires diagnostic accuracy along with excellent interobserver reproducibility.

Evaluation of Fine Needle Aspiration Cytopathology in Salivary Gland Tumors under Milan System: Challenges, Misdiagnosis Rates, and Clinical Recommendations

(1) Background: Salivary gland tumors are rare in the head and neck. To determine the need and extent of surgical intervention, fine needle aspiration (FNA) is a widely accepted tool to approach salivary gland lesions. However, the FNA cytology varies between entities, while the lack of uniform terminology makes diagnosis more challenging. Since establishing the Milan system for reporting salivary gland cytopathology (MSRSGC) has become an increasingly accepted reporting standard, further examination and detailed recommendations were needed. (2) Methods: Between April 2013 and October 2021, 375 cases with FNA and salivary gland resection were retrospectively collected. All FNA specimens were reclassified according to the criteria of MSRSGC. After surgical excision, the FNA data were compared with the histological diagnosis to estimate the risk of malignancy (ROM), the risk of neoplasm (RON), and the diagnostic accuracy for each diagnostic category. (3) Results: Our cohort's distribution of ROM and RON was similar to the MSRSGC's recommendation. Carcinoma ex pleomorphic adenoma (CXPA) has the highest rate (66.7%) of misdiagnosed as a nonneoplastic lesion or benign salivary gland tumor. Pleomorphic adenoma (PA) and Warthin's tumor were the most common benign salivary gland tumors, while the cytology diagnosis of Warthin's tumor seems more challenging than PAs. (4) Conclusions: Despite the convenience and effectiveness of MSRSGC, we suggest close follow-up, re-biopsy, or surgical removal for salivary lesions even in Milan IVA-Benign for possibly missing FNA of malignancy, mixed lesions, or prevention of malignant transformation.

Salivary gland fine-needle aspiration biopsy: quality assurance results from a tertiary cancer center

INTRODUCTION

Fine-needle aspiration biopsy (FNAB) plays a critical role in the management of patients with salivary gland lesions. A specific diagnosis can be difficult due to the wide range of lesions with overlapping morphologic features, potentially leading to interpretation errors. We analyzed the cytologic-histologic discrepancies identified in the quality assurance program of a major cancer center in cases of salivary gland FNAB and performed a root cause analysis.

MATERIALS AND METHODS

Salivary gland FNAB specimens performed during a 12-year period at a major tertiary cancer center were reviewed. The inclusion criteria for this study included FNAB cases of salivary glands with subsequent histologic or flow cytometry follow up. The cytologic diagnoses for these cases were recategorized according to the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) based on the original reports. The risk of neoplasm and malignancy based on the cases with subsequent resection or flow cytometry and the most common causes of discrepancy were analyzed.

RESULTS

The risk of neoplasm ranged from 41% to 99% and the risk of malignancy ranged from 22% to 99% among the different MSRSGC categories. Lymphoid and myoepithelial rich lesions were the most common miscategorized lesions using the MSRSGC. Reactive changes due to inflammation were associated with overcalls. The most common malignancy in the atypical category was mucoepidermoid carcinomas.

CONCLUSIONS

Myoepithelial and lymphoid rich lesions arising in the salivary gland are associated with a higher risk of misclassification. The use of category IVB in the MSRSGC is appropriate for lesions with abundant myoepithelial cells. Reactive atypia seen in sialadenitis was the most common feature associated with overcall.

Assessment of Risk of Malignancy of Fine-needle Aspiration Cytology in Salivary Gland Lesions Using the Milan System for Reporting Salivary Gland Cytopathology Categorization: A Systematic Review and Meta-analysis

BACKGROUND

Fine-needle aspiration cytology (FNAC) of the salivary gland is crucial in the identification of salivary gland lesions, but the variation in morphological pattern and the overlap of morphological traits can result in erroneous interpretation and affect treatment, making FNAC of the salivary gland problematic. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was created to address these problems.

OBJECTIVES

To ascertain whether the FNAC method using MSRSGC was reliable in predicting the risk of malignancy (ROM) in each category of salivary gland lesions.

MATERIALS AND METHODS

The databases PubMed-MEDLINE, Web of Science, Cochrane, Scopus, and Google Scholar were all searched using pertinent keywords, reference searches, and citation searches. A fixed effect model was used to determine the pooled proportion with a 95% confidence interval (CI). All statistical analyses were performed using Meta Disc and R version 4.0.2 (R Foundation for Statistical Computing).

RESULTS

After reviewing the submissions' abstracts and titles, 58 documents that satisfied the necessary inclusion and exclusion criteria were ultimately selected. A total of 19,652 samples from 19,408 individuals was analyzed, out of which 9,958 samples were available for histopathological follow-up. The pooled ROM for category I was 10%, category II was 5%, category III was 28%, category IV A was 2%, Category IV B was 34%, category V was 91%, and category VI was 99%.

CONCLUSION

Milan System for Reporting Salivary Gland Cytopathology is useful for risk stratification and quality control, confirming its validity and diagnostic utility. Widespread use of MSRSGC would improve the accuracy of salivary gland cytology and lead to better patient care and improved treatment strategies. The results of this study are in consonance with reported values as per MSRSGC except for category V.

CLINICAL SIGNIFICANCE

The MSRSGC which was first reported in 2018 is a very useful tool for proper stratification of ROM in salivary gland FNAC. This study allowed us to validate the ROM values in different categories as reported in MSRSGC.

Nondiagnostic category of Milan System for Reporting Pediatric Salivary Gland Cytopathology: outcomes and root cause analysis

BACKGROUND

Fine-needle aspiration (FNA) results classified as the nondiagnostic category of the Milan system for reporting salivary gland cytopathology (MSRSGC) may be infrequently encountered in children. Clinical management may be challenging due to lack of data regarding outcomes and underlying causes.

METHODS

We retrospectively analyzed 106 consecutive pediatric salivary gland FNAs (2000-2020; 45% performed under image guidance). The outcomes of patients with nondiagnostic results were analyzed. Clinical parameters, FNA procedural parameters, and histopathologic parameters were compared between diagnostic and nondiagnostic cases. A root cause analysis was performed using the fishbone diagram and the 5 Whys method.

RESULTS

A total of 103 initial FNAs were identified. The nondiagnostic rates for initial and repeat biopsy were 16% (16/103) and 67% (2/3), respectively. Initial nondiagnostic FNAs were most frequently managed by clinical/radiologic follow-up only (56%, 9/16), followed by direct surgery (19%, 3/16) and repeat FNA (19%, 3/16). By histologic and clinical/radiologic follow-up, the risk of malignancy for nondiagnostic cases was zero. Palpation guidance (P < .05), inadequate sampling determined by rapid on-site evaluation (P < .01), and lesions with cystic, vascular, or diffuse nature (P < .05) were significantly associated with nondiagnostic results. By root cause analysis, proceduralist sampling error and lack of ultrasound guidance were the most common primary and secondary causes, respectively.

CONCLUSIONS

Pediatric salivary gland lesions of the nondiagnostic MSRSGC category have minimal risk of malignancy and may be successfully managed by clinical/radiologic follow-up. The root causes for nondiagnostic results were often multifactorial and primarily related to proceduralist sampling, characteristics of the lesions, and lack of ultrasound guidance.

The Milan System for Reporting Salivary Gland Cytopathology

OBJECTIVES

Our study assesses whether the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) offers any benefit over the original cytology classification, and measures interobserver agreement.

METHODS

Four cytopathologists retrospectively blindly classified preoperative cytology by MSRSGC from 101 resected salivary tumors. Consensus MSRSGC diagnoses were correlated with surgical pathology diagnoses and compared with the original cytology classification. Diagnostic parameters were calculated for both systems. Interobserver variability was assessed.

RESULTS

The original cytology classification vs MSRSGC had sensitivity, specificity, positive predictive value, and negative predictive value of 75.0% vs 78.3%, 97.1% vs 98.0%, 91.2% vs 94.7%, and 90.1% vs 90.0%, respectively. The original cytology classification risk of neoplasm (RON) was 91.7% for "negative for malignancy" and 100.0% for other categories. The MSRSGC RON was 71.4% in category II (nonneoplastic) and 100.0% in all other categories. The original cytology classification risk of malignancy (ROM) ranged from 0.0% for "atypical" to 100.0% for "positive for malignancy." The MSRSGC ROM ranged from 0.0% in categories I (nondiagnostic) and III (nonneoplastic) to 100.0% in category VI (malignant). Weighted agreement using the MSRSGC was 92% (Gwet AC1, 0.84); unweighted agreement was 69% (Gwet AC1, 0.64). MSRSGC category IVA (benign neoplasm) was most likely to show interobserver agreement, with complete agreement in 67% of cases.

CONCLUSIONS

The MSRSGC performs similarly to the original cytology classification and shows relatively high interobserver agreement.

Nondiagnostic salivary gland FNAs are associated with decreased risk of malignancy compared with "all-comer" patients: Analysis of the Milan System for Reporting Salivary Gland Cytopathology with a focus on Milan I: Nondiagnostic

BACKGROUND

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) reports a 25% rate of malignancy (ROM) for the Milan I: Nondiagnostic (ND) category. We clarify the ROM of ND salivary gland fine-needle aspirations (SGFNAs) based on our institutional experience and review of the literature.

METHODS

Overall risk of malignancy (OROM) and that for those with surgical/flow cytometric follow-up (FROM) for each category and "all-comers" were calculated for Emory SGFNAs from January 2010 through March 2021. From a literature review of 50 articles using MSRSGC, distribution of diagnoses, rates of follow-up, FROM, and OROM by category were calculated. FROMs and OROMs between ND FNAs and all-comers were compared. Milan I rate was compared with the ratio of Milan I OROM to all-comer OROM.

RESULTS

Of 819 SGFNAs at Emory, 12.8% (n = 105/819) were ND. Thirty-two had known follow-up, with 12 (37.5%) being malignant. Nonmucinous cyst contents accounted for 26.7% of ND SGFNAs (n = 28/105); all 7 with surgical follow-up were benign. Of 50 MSRSGC studies, 18.2% (n = 2384/13,129) of SGFNAs were classified as ND, 26.6% (n = 635/2384) with known follow-up. Total FROM and OROM for ND FNAs (15.7% and 4.1%, respectively) were significantly lower than those for all-comers (24.9% and 11.4%, respectively) (p < .001). There was no relationship between rate of ND SGFNA and ND ROM.

CONCLUSIONS

The ND category is associated with a lower ROM than that of all-comer SGFNA patients. The "true" ROM for ND SGFNAs is likely best estimated by the 4.1% OROM. SGFNAs showing nonmucinous cyst contents have a particularly low ROM. Rate of ND SGFNAs does not influence ND ROM.

Utility of the Milan System for Reporting Salivary Gland Cytology, with focus on the incidence and histologic correlates of atypia of undetermined significance (AUS) and salivary gland neoplasm of uncertain malignant potential (SUMP): A 3-year institutional experience

BACKGROUND

Fine-needle aspiration (FNA) is the preferred diagnostic test for salivary gland lesions. The purpose of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is to standardize salivary gland cytology reporting and guide treatment decisions. The objective of the current study was to evaluate the utility and performance of the MSRSGC, with a focus on the cytomorphology of lesions diagnosed as atypia of undetermined significance (AUS) and salivary gland neoplasm of uncertain malignant potential (SUMP).

METHODS

In total, 123 salivary gland FNAs were included in the study. FNA diagnoses for all cases were reviewed and recategorized, as applicable, according to the MSRSGC. Cytohistologic correlation was performed in 51 cases that had available surgical follow-up, and the risk of malignancy (ROM) was calculated.

RESULTS

Most FNA samples were from the parotid gland. The mean patient age was 61.4 years, and the male-to-female ratio was 1.3:1. The ROM was 0% (categories I and II; nondiagnostic and benign nonneoplastic, respectively), 50% (category III; AUS), 0% (category IVA; benign neoplasm), 40% (category IVB; SUMP), 100% (category V; suspicious for malignancy), and 100% (category VI; malignant). Sensitivity, specificity, positive predictive value, and negative predictive value were 100% each. In addition, the primary factors for an AUS diagnosis were identified as low cellularity and/or the presence of lymphocytes. The presence of oncocytes followed by cellular atypia in an otherwise classic pleomorphic adenoma were principal factors for a SUMP diagnosis.

CONCLUSIONS

The authors report an ROM comparable to that reported in the literature, with a sensitivity and specificity of 100%, supporting adaptation of the MSRSGC into the system for reporting salivary gland cytology. In addition, the findings emphasize the need to refine criteria for AUS and SUMP, thereby improving the predictive capability and subsequent management of salivary gland lesions.