Cytopathology of benign sebaceous salivary gland neoplasia: Comparison of two analogous yet dissimilar entities

INTRODUCTION

Benign sebaceous salivary gland (SG) neoplasms represent approximately 0.2% of all salivary gland neoplasms. Not only are fine needle aspiration (FNA) biopsy findings of sebaceous adenoma (SA) and sebaceous lymphadenoma (SLA) limited, but their findings are also rarely compared with one another.

MATERIALS AND METHODS

Our cytopathology files were searched for examples of benign sebaceous SG neoplasms with concomitant histopathological verification. FNA biopsy and cell collection were performed using standard technique.

RESULTS

One case each of parotid SA and parotid SLA showed markedly dissimilar cytomorphology. The SA case was composed of a repetitive population of profusely multivacuolated polygonal cells with single and multiple nuclei, and was specifically recognised cytologically as a sebaceous neoplasm due to its characteristic cytoplasmic vacuolisation. The SLA case, however, was characterised by smears filled primarily with lymphocytes and only scant widely scattered basaloid cell clusters. A non-specific diagnosis of basaloid neoplasm was rendered. In retrospect, recognition of sebaceous differentiation was limited to rare cell groups.

CONCLUSION

Though nominally, epidemiologically, and to a degree histopathologically analogous, the cytopathology of SA and SLA are markedly dissimilar, reflecting the dominant cell component in each. With FNA biopsy, a specific interpretation is more likely for SA than SLA due to the overwhelming obscuring lymphoid population in the latter.

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.

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.

Multi-institutional validation of a modified scheme for subcategorizing salivary gland neoplasm of uncertain malignant potential (SUMP)

BACKGROUND

The salivary gland neoplasm of uncertain malignant potential (SUMP) category in the Milan System is diagnostically challenging. This study aims to validate a modified scheme for subcategorizing SUMP in a large multi-institutional cohort.

METHODS

Retrospective review of salivary gland fine-needle aspirations (FNAs) from 10 institutions were classified based on the Milan System. Cases diagnosed as SUMP with available cytology slides and surgical follow-up were retrieved for review and subcategorized based on a modified scheme as follows: basaloid SUMP (B1: absent/scant nonfibrillary matrix; B2: presence of nonfibrillary/mixed-type matrix), oncocytic/oncocytoid SUMP (O1: with mucinous background; O2: without mucinous background), and SUMP not otherwise specified (NOS).

RESULTS

A total of 742 (7.5%) cases from 9938 consecutive salivary gland FNAs were classified as SUMP. Among them, 525 (70.8%) had surgical follow-up and 329 (62.7%) were available for review. The overall risk of malignancy (ROM) of SUMP was 40.4%. There were 156 cases (47.4%) subcategorized as basaloid SUMP with a ROM of 36.5%, 101 (30.7%) as oncocytic/oncocytoid SUMP with a ROM of 52.5%, and 72 (21.9%) as SUMP NOS with a ROM of 31.9%. The ROM of oncocytic/oncocytoid SUMP was significantly higher than basaloid SUMP (P = .0142) and SUMP NOS (P = .0084). No significant differences in ROM were noted between B1 and B2 (36.7% vs 36.4%, P = 1.0000) and O1 and O2 (65.2% vs 48.7%, P = .2349).

CONCLUSIONS

The ROM of oncocytic/oncocytoid SUMP was 52.5% and significantly higher than that of basaloid SUMP (36.5%, P = .0142) and SUMP NOS (31.9%, P = .0084), whereas no significant differences in ROM were noted for cases with different types of extracellular matrix or background material.

Salivary gland neoplasms with basaloid features in the era of the Milan system for reporting salivary gland cytology: Classification and interobserver agreement

BACKGROUND

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) has been shown to have moderate to good reproducibility for categorization of salivary gland fine-needle aspiration (FNA) specimens. Less is known of its accuracy and interobserver reproducibility for categorization of the diagnostically difficult group of basaloid neoplasms.

METHODS

Forty-five salivary gland specimens with a basaloid morphology (pleomorphic and monomorphic adenomas and adenoid cystic carcinomas) were independently assigned by seven cytopathologists to one of the MSRSGC categories. Interobserver agreement was assessed for average agreement, chance expected agreement and by Cohen's κ and diagnostic accuracy. Correlation of the salivary gland neoplasm of unknown malignant potential (SUMP) category with histologic diagnosis and benign or malignant designation along with interobserver reproducibility were calculated.

RESULTS

Average observed agreement for assignment to the MSRSGC was 46% and Cohen's κ = 0.2%. The SUMP category did not correlate with tumor type or with the benign or malignant nature of the neoplasm. Diagnostic specificity and sensitivity were 92% and 100% for consensus diagnosis, but were 76% and 77% for individual diagnoses.

CONCLUSION

The interobserver agreement in categorizing basaloid neoplasms by the MSRSGC is poorer than for salivary gland lesions overall. This reflects the difficulty in diagnosing basaloid neoplasms. Nonetheless, diagnostic accuracy appears similar to that of salivary gland neoplasms as a whole.

Glial Fibrillary Acidic Protein Expression Helps Distinguish Pleomorphic Adenoma from Histologic Mimics

Pleomorphic adenoma (PA) is the most common biphasic type of salivary gland tumour to arise in adults. It is a biphasic tumour composed of both luminal (ductal) cells and abluminal (basal and myoepithelial) cells. Other biphasic salivary gland type tumours, both benign and malignant, can mimic PA, especially on small biopsies. Previous studies have shown that glial fibrillary acidic protein (GFAP) is preferentially expressed in PA and can be useful in the distinction from other salivary gland tumours. However, most of these studies were performed on a small subset of tumour types at a time when the classification of salivary gland type tumours was less refined. The purpose of this study was to assess the expression of glial fibrillary acidic protein (GFAP) in a broad group of both benign and malignant salivary gland tumours. The expression of GFAP was assessed in 99 tumours including 54 PAs, 5 basal cell adenomas, 1 myoepitheliomas, 5 adenoid cystic carcinomas, 6 epithelial-myoepithelial carcinomas (EMCA), 6 mucoepidermoid carcinomas, 7 salivary duct carcinomas, 1 adenocarcinomas NOS, 2 myoepithelial carcinomas, 4 basal cell adenocarcinomas, 5 acinic cell carcinomas and 3 polymorphous adenocarcinomas. Of the malignant cases, 8 were classified as carcinomas ex PA. GFAP was also assessed in 19 concurrent biopsy specimens. GFAP was expressed in the resections of 51 PAs examined (94%). Expression was predominantly strong and diffusely seen in myoepithelial cells. Strong and diffuse GFAP expression was also seen in two EMCAs (33%) and one myoepithelial carcinoma (50%). On biopsy specimens, 100% of PAs and basal cell adenomas expressed GFAP. GFAP was also seen in 1 out of 3 carcinomas ex PAs on biopsies. Almost all PAs show strong and diffuse expression of GFAP. In contrast, most malignant neoplasms that can mimic PA on biopsies show only rare, focal expression. Other benign tumours composed of abluminal/myoepithelial cells also show focal expression of GFAP, highlighting the spectrum these tumours share with PA. Overall, the presence of strong and diffuse GFAP expression can favour a benign neoplasm, specifically a PA, on limited biopsy specimens.

Histopathological Review of Diagnostic Categories of the Milan System for Reporting Salivary Gland Cytopathology - An Institutional Experience of 6 Years

Introduction:

Salivary gland malignancies account for 2 to 4% of head and neck cancers. Fine needle aspiration cytology (FNAC) is used in preoperative diagnosis of salivary gland lesions. Although FNAC is a highly reliable technique for preoperative diagnosis, there were no consensus on salivary gland cytopathology reporting. Recently, an international group has recommended a classification system for salivary gland FNAC reporting titled “Milan System for Reporting Salivary Gland Cytopathology” (MSRSGC). In this study, we aimed to evaluate the usability of the Milan System, its ability to determine the risk of malignancy for each category, with comparisons of inital cytologic and final histopathological diagnosis.

Materials and Methods:

We performed a retrospective analysis of salivary gland lesion FNAC in our department from 2013 to 2019. A total of 578 FNACs were performed in 514 patients. Of these, 85 cases had surgical follow-up (parotid gland, n = 73, submandibular gland, n = 12). The cytological samples were categorized according to the MSRSGC into six categories by two pathologists. The risk of malignancy (ROM) and diagnostic accuracy values were calculated for each diagnostic categories.

Results:

A total of 85 aspirates of the patients with follow-up, the MSRSGC diagnostic categories were as follows: non-diagnostic in 7 aspirates (8.2%), non-neoplastic in 3 (3.5%), atypia of undetermined significance (AUS) in 9 (10.5%), benign neoplasm in 43 (50.5%), salivary gland neoplasm of undetermined malignant potential in 7 (8.2%), suspicious for malignancy in 10 (11.7%), and malignant in 6 (7%). The ROM for each category was 28, 5%, 0%, 33%, 0%, 28.5%, 90%, and 100%, respectively.

Conclusion:

FNAC plays a critical role in the evaluation of patients with salivary gland lesions. The MSRSGC helps in the standardization of the process of diagnosis and clinical management of salivary gland lesions, especially of AUS and SUMP categories that are indeterminate categories in nature.

Metastatic malignant melanoma mimicking a salivary gland basaloid neoplasm after treatment with nivolumab

Malignant melanoma is a well-known diagnostic pitfall, given its propensity to metastasize to different sites and mimic various entities. In this report, we present a fine-needle aspiration biopsy (FNA) of a metastatic melanoma with basaloid features that is occurring in the preauricular/parotid area. The patient is a 17-year-old male with a history of excision of melanoma of the left temple, and was undergoing adjuvant treatment with nivolumab. The prior excision was positive for S100, HMB-45, melan-A, and tyrosinase. On follow-up, he presented with non-FDG avid left preauricular area lesions. FNA was performed, and on-site evaluation demonstrated a cellular basaloid neoplasm with focal fibrillary stroma. Immunohistochemical stains revealed that the tumor cells were positive for SOX-10, S100, MITF, and HMGA2, and were negative for HMB-45, melan-A, tyrosinase, p63, cam 5.2 and PLAG1. The positive S100, SOX-10, and MITF results and negative cam 5.2 result supported the diagnosis of melanoma. Nivolumab was then stopped, Dabrafenib/Trametinib were started, and the patient underwent excision of the nodules. Nine-months later, he developed a rib metastasis that was positive for S100, SOX-10, melan-A, and tyrosinase. This report emphasizes that melanoma involving the parotid gland region has the potential to be misdiagnosed by FNA as a salivary gland neoplasm because of overlapping cytologic features and immunophenotypes. This pitfall is avoided by careful morphologic analysis and judicious use of ancillary studies.

Analysis of the risk of malignancy associated with the basaloid and oncocytic subtypes of the salivary gland neoplasm of unknown malignant potential (SUMP) category in the Milan system

BACKGROUND

The salivary gland neoplasm of unknown malignant potential (SUMP) category reflects the cytomorphologic overlap and complexity of reporting salivary gland cytology in the Milan system. It includes neoplasms for which a diagnosis of a specific entity cannot be made and, more importantly, for which a carcinoma cannot be entirely excluded. For risk stratification, the subcategorization of SUMP based on the predominant cell type is recommended. This study was aimed at evaluating the risk of neoplasm (RON) and the risk of malignancy (ROM) of the basaloid and oncocytic subtypes of the SUMP category.

METHODS

A retrospective analysis of 482 salivary gland fine-needle aspirations from 2012 to 2019 resulted in 48 SUMP cases. The cytology of these cases was reviewed and reclassified as the basaloid or oncocytic subtype. Surgical follow-up was available for 36 cases. The RON and ROM for each subtype were calculated.

RESULTS

The RON and ROM were 100% and 23%, respectively, for monomorphic basaloid tumors and 88% and 58.8%, respectively, for monomorphic oncocytic tumors. The ROM for basaloid tumors was 8.3% without matrix/with minimal matrix and 60% with an nonfibrillary matrix. The ROM for oncocytic tumors was 50% without a cystic background and 60% with a cystic or mucinous background. The difference was not statistically significant for either of the subgroups.

CONCLUSIONS

Even though statistically not significant in our study, the differential ROMs within the oncocytic and basaloid subgroups help in the risk stratification of SUMP cases. Further subcategorization based on the stroma and background helps in limiting the differential diagnosis but does not necessarily add to the value of the risk stratification.

Thyroid sclerosing mucoepidermoid carcinoma with eosinophilia in conjunction with parotid basal cell adenoma: Cytologic, histologic, and molecular features

Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is a rare malignancy in the thyroid: only 56 cases with histologic descriptions are reported in the literature and fewer reports describe the cytomorphology. Given the rarity of SMECE, data on the cytomorphologic and molecular features are limited. We report a case of a 53-year-old woman with a 5 cm left thyroid mass. Fine-needle aspiration (FNA) revealed atypia of undetermined significance and pathology of left thyroid lobectomy specimen showed SMECE. Additionally, a left pre-auricular lump was noted and FNA followed by left superficial parotidectomy showed basal cell adenoma. Next-generation sequencing showed point mutations in NTRK3 and NF1. Unlike salivary gland mucoepidermoid carcinoma, MAML2 translocations are not present in SMECE. Even though it is a rare entity, awareness of SMECE of the thyroid is important. In this case report we review the cytomorphologic, histologic, and molecular features.

The cytology of salivary gland neoplasms with globules of extracellular matrix: Case-based review of adenoid cystic carcinoma and its potential mimics

Fine needle aspiration (FNA) cytology is an important tool for diagnosing salivary gland neoplasms and for guiding clinical management. The classic adenoid cystic carcinoma (AdCC) is a basaloid neoplasm with abundant extracellular matrix. The presence globules of extracellular matrix are quite characteristic of AdCC but not diagnostic. We selected from our files six FNA cases that contained at least some globules of amorphous matrix that are similar to the ones seen in AdCC. The aim of this case-based review is to discuss the pitfalls and some of the common differential diagnoses of AdCC in FNA cytology. By the end of this review, we hope to have shared with the readers the lessons we learned from these cases and to highlight the key criteria needed to make a correct diagnosis of AdCC based on cytomorphology. The importance of considering other entities, in addition to AdCC, whenever a salivary gland FNA presents with globules is emphasized.

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

BACKGROUND

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) represents a standardized reporting system for salivary gland lesions. The recent literature has demonstrated a wide range of data regarding range of malignancy (ROM) and interobserver variability. The objective of the current study was to evaluate the reproducibility and interobserver agreement of MSRSGC, and establish the ROM in a unique patient population residing within a designated Health Professional Shortage Area.

METHODS

A total of 380 salivary gland fine-needle aspiration cases were obtained over a 3-year period. Corresponding cytology reports and slides were reviewed in a blinded fashion by a panel of cytopathologists and recategorized using MSRSGC. ROM was calculated by cytohistologic correlation in 176 cases. Agreement between review of reports and slides and interobserver reliability were determined using kappa statistics.

RESULTS

The ROMs per MSRSGC category based on review of reports and slides were as follows: 4% and 0%, respectively, for nonneoplastic; 22% and 0%, respectively, for nondiagnostic; 42.9% and 48%, respectively, for atypia of undetermined significance; 1.6% and 1.9%, respectively, for benign-neoplastic; 17.9% and 15.6%, respectively, for salivary gland neoplasm of uncertain malignant potential; 81.8% and 71.4%, respectively, for suspicious for malignancy; and 100% and 90.5%, respectively, for malignant. There was a 59.2% overall agreement between review of reports and slides with regard to recategorizing salivary gland lesions (kappa, 0.51). The interobserver reliability demonstrated a 64.6% agreement (weighted kappa, 0.59).

CONCLUSIONS

The ROMs at the study institution appeared comparable to those in the published literature. There was moderate overall agreement among cytopathologists and low interobserver agreement with regard to the indeterminate categories. Image-guided fine-needle aspiration specimens; rapid onsite adequacy; and integration of clinical, imaging, and ancillary studies can improve diagnostic accuracy among indeterminate lesions.

Salivary gland fine-needle aspiration cytology with the application of the Milan system for risk stratification and histological correlation: A retrospective 6-year study

BACKGROUND

The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) is based on risk stratification. We presented our experience with fine-needle aspiration cytology (FNAC) for the diagnosis of salivary glands lesions by applying the MSRSGC categorization to the cytological diagnoses, and determined risk of malignancy (ROM) for each category.

METHODS

Fine-needle aspiration cytology of salivary gland lesions performed over a 6-year period was retrieved. FNAC results were retrospectively categorized according to the MSRSGC criteria, and correlated with corresponding histologic follow-up. ROM for each diagnostic category was calculated.

RESULTS

A total of 208 FNAC of salivary gland lesions were reviewed and retrospectively categorized as: non-diagnostic (ND) 23 (11%), non-neoplastic (NN) 54 (26%), atypia of undetermined significance (AUS) 10 (4.8%), benign neoplasms (BN) 77 (37%), salivary gland of uncertain malignant potential (SUMP) 13 (6.3%), suspicious for malignancy (SM) 7 (3.4%), and malignant (M) 24 (11.5%). Histopathological follow-up was available for 84 of 208 cases (40.4%). Overall concordance rate between FNAC and histology was 78.8%. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated as 93.3%, 94.6%, 82.4%, and 98.2%, respectively. Diagnostic accuracy to distinguish benign from malignant disease was 94.4%. ROM for each category was ND 0%, NN 0%, AUS 75%, BN 2.2%, SUMP 28.6%, SM 50%, and M 100%.

CONCLUSION

Fine-needle aspiration cytology continues to be an accurate diagnostic tool for most salivary gland neoplasms showing classical morphologic features. However, difficult cases with unusual or overlapping features will occur. In these situations, the use of MSRSGC risk-stratification could be helpful to define appropriate management.