Milan System for Grading Salivary Gland Cytopathology

Educational Objectives

The goal of this program is to improve management of salivary gland disease. After hearing and assimilating this program, the clinician will be better able to:

1. Choose a method of biopsy for salivary gland tumors.
2. Use established classification systems to report thyroid and salivary gland cytopathology.
3. Correlate findings on imaging with probable lesion status.

Summary

Introduction: the Bethesda classification is used for reporting thyroid cytopathology; the Milan system for reporting salivary gland cytopathology is used to report salivary gland disease

Milan system categories: 1 is non-diagnostic, and may indicate insufficient material for cytopathologic examination; 2 is non neoplastic, ie, the pathology is benign (inflammatory origin); 3 refers to atypia of undetermined significance (AUS) which is similar to the Bethesda category; category 4 is divided into 2 sub-categories; 4A refers to benign lesions, eg, pleomorphic adenoma, Warthin tumor, and 4B indicates salivary gland neoplasm of uncertain malignant potential (SUMPs); 5 is suspicion of malignancy; 6 is malignant; the Milan system helps evaluate the risk for malignancy in salivary gland lesions; even with nondiagnostic samples, the risk of malignancy is 0.25%; cytopathology and parotid sampling is challenging because of the many different tumor types which are difficult to categorize; AUS is associated with a risk of 20% for malignancy

Evaluation of salivary gland tumors: clinicians should assess patient presentation for clinical signs and symptoms; the quality of radiographic imaging plays a crucial role in diagnosis; diagnosis should not be based on computed tomography (CT) alone; magnetic resonance imaging (MRI) with diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping provides the most information for salivary gland tumors; cytopathology may help in decision making

Patient history: concerning features include progressive rapid growth, pain (including referred pain), numbness, progressive facial weakness, bruises, facial swelling, and history of tumor removal; intraparotid lymph node metastasis from skin cancer is common in patients >70 yr of age with previous history of treatment for skin cancer

Examination: the clinician must determine with palpation whether the lesion is fixed or mobile, eg, a large pleomorphic adenoma behind the angle of the mandible is more likely to be fixed; contours of most benign tumors are well defined because they are encapsulated; the clinician must take notice of the skin overlying the lesion, induration, and fixation; cranial nerves and lymph nodes must be examined; watch for signs of paralysis and trismus; evaluation for neck masses must be performed; lymph node vs neck mass — the lymphatic drainage for the parotid gland occurs through upper level V, external jugular nodes, level II and level 1B

Imaging: ultrasonography (US) may help in determining the involvement of the parotid gland, even in patients with apparent neck masses; CT may reveal most salivary gland tumors and lymph nodes; CT is useful for the evaluation of suspicious lymph nodes; MRI with DWI and ADC shows the density of the lesion, the capsule, and potential infiltration, but may be misleading in cases of inflammatory lesions; MRI with DWI and ADC is very helpful overall for identification of salivary gland tumors; MRI is generally readily available, but obtaining a good quality thin cut MRI with proper windowing for the parotid is more difficult; the DWI and ADC values are reported by the radiologist; capsulation can be clearly ascertained in most benign lesions; malignancies may appear darker on the ADC mapping

Biopsy: most patients can undergo in-office biopsy; fine needle aspiration cytology (FNAC) may return as indeterminate biopsies because of insufficient tissue; obtaining more tissue with better quality is possible with US guidance; core biopsies for the parotid gland have a very low risk of seeding and essentially 0% risk for facial nerve injury; sensitivity and specificity of FNAC for salivary gland tumors is good; all cytopathologic classifications have some variability; suspicion for malignancy is high in cases with AUS, SUMPs, suspicion of malignancy, and malignancy; cytopathologists may be requested to provide cytopathologic descriptions and a differential diagnosis in addition to the Milan classification

Future directions: molecular testing for fusion proteins may aid in diagnosing secretory carcinomas and adenoid cystic carcinoma, but it is not yet commercially available; molecular changes help clarify lesions that are cytopathologically dedifferentiated or have histologic overlap; diagnosis is based on history, examination, radiologic and cytopathologic features

Management: management of the facial nerve during parotid gland surgery is important; superficial tumors located away from the main trunk of the facial nerve can be comfortably resected; the clinician may perform a retrograde dissection to expose distal branches; extracapsular dissection may be completed for superficial tumors; the facial nerve may be monitored with 4 electrodes on the frontalis, orbicularis oculi, orbicularis oris, and mentalis; the speaker prefers not to perform a total resection for malignancies; most patients undergo radiation therapy in addition to surgery; thin cut MRI helps visualize the facial nerve; sequential MRI is performed at certain centers to locate the exit of the facial nerve; 1.5 T imaging is useful for the parotid gland; 3T imaging is useful for skull base invasion and perineural invasion; DWI protocol must be obtained

Readings

Bhushan R, Priyadarshini Shrivastava J, Verma V. Application of the Milan system for reporting salivary gland cytology: A prospective study. Iran J Pathol. 2023;18(4):439-448. doi:10.30699/IJP.2023.199632.3098; Cibas ES, Ali SZ. The 2017 Bethesda system for reporting thyroid cytopathology. Thyroid. 2017;27(11):1341-1346. doi:10.1089/thy.2017.0500; Gandhi M, Sommerville J. The imaging of large nerve perineural spread. J Neurol Surg B Skull Base. 2016;77(2):113-123. doi:10.1055/s-0036-1571836; Joudeh AA, Shareef SQ, Al-Abbadi MA. Fine-needle aspiration followed by core-needle biopsy in the same setting: Modifying our approach. Acta Cytol. 2016;60(1):1-13. doi:10.1159/000444386; Kala C, Kala S, Khan L. Milan system for reporting salivary gland cytopathology: An experience with the implication for risk of malignancy. J Cytol. 2019;36(3):160-164. doi:10.4103/JOC.JOC_165_18; Lewis AG, Tong T, Maghami E. Diagnosis and management of malignant salivary gland tumors of the parotid gland. Otolaryngol Clin North Am. 2016;49(2):343-380. doi:10.1016/j.otc.2015.11.001; Phulware RH, Sardana R, Chauhan DS, Ahuja A, Bhardwaj M. Extracranial schwannomas of the head and neck: A literature review and audit of diagnosed cases over a period of eight years. Head Neck Pathol. 2022;16(3):707-715. doi:10.1007/s12105-022-01415-y; Singh G, Jahan A, Yadav SK, et al. The Milan System for Reporting salivary gland cytopathology: An outcome of retrospective application to three years' cytology data of a tertiary care hospital. Cytojournal. 2021;18:12. Published 2021 May 6. doi:10.25259/Cytojournal_1_2021; Steuer CE, Hanna GJ, Viswanathan K, et al. The evolving landscape of salivary gland tumors. CA Cancer J Clin. 2023;73(6):597-619. doi:10.3322/caac.21807; To VS, Chan JY, Tsang RK, et al. Review of salivary gland neoplasms. ISRN Otolaryngol. 2012;2012:872982. Published 2012 Feb 16. doi:10.5402/2012/872982.

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Mydlarz was recorded at the Tenth Annual Atlantic Otolaryngology-Head and Neck Surgery Update, held February 17-18, 2024, in Pompano Beach, FL, and presented by The Johns Hopkins University School of Medicine. For information on upcoming CME activities from this presenter, please visit https://hopkinscme.cloud-cme.com. Audio Digest thanks Dr. Mydlarz and The Johns Hopkins University School of Medicine for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0.75 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0.75 CE contact hours.

Lecture ID:

OT571102

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.