An Underappreciated Cytomorphological Feature of Secretory Carcinoma of Salivary Gland on Fine Needle Aspiration Biopsy: Case Report with Literature Review

Molecular testing in salivary gland cytopathology: A practical overview in conjunction with the Milan system

Recently, significant advances in the molecular characterization of salivary gland neoplasms have facilitated the classification and diagnosis of specific diagnostic entities. In the highly challenging diagnostic scenario of salivary malignancies, molecular testing is increasingly being adopted in routine practice to refine the cytological diagnosis of salivary lesions. Here, we reviewed the most recent evidence in the field of salivary glands molecular cytopathology.

Salivary Gland Secretory Carcinoma; Review of 13 Years World-Wide Experience and Meta-Analysis

OBJECTIVES

Secretory Carcinoma is a malignant salivary gland tumor, initially described in 2010. This rare tumor is associated with the translocation t(12;15) (p13;q25), resulting in the fusion gene ETV6-NTRK3. Since this tumor is quite rare, most publications describe only small cohorts of patients. We aimed to investigate the clinical, pathological, and prognostic features of this newly defined malignant entity.

DATA SOURCES

Pubmed, Google Scholar, and Web of Science databases.

REVIEW METHODS

All published articles between 2010 and 2023 were reviewed. Search terms included the terms "Mammary Analogue Secretory Carcinoma" and "Secretory Carcinoma". All articles published in English reporting on Secretory Carcinoma of salivary glands were retrieved.

RESULTS

One-hundred and 12 retrospective articles reporting a total of 674 patients were included, with 52% males and a mean age of 44.9 ± 18.9. The event rate for patients with advanced-stage disease (Stage 3/4) at presentation was 24.1% (95% CI 17.6%-31.9%, I2  = 9.2%), 14.6% for regional metastases (95% CI 10.5%-20%, I2  = 12%), and the event rate of distant metastasis was 8.4% (95% CI 5.5%-12.7%, I2  = 4.2%). Adjuvant radiotherapy was administered for 30.3% of patients (95% CI 24.1%-37.2%, I2  = 21.5%). The recurrence rate was 19% (95% CI 15.1%-23.8%, I2  = 5%). Survival outcomes showed a 17.2% death of disease rate for Secretory Carcinoma patients (95% CI 13.5%-21.8%, I2  = 7.3%).

CONCLUSIONS

Secretory Carcinoma is a rare and relatively newly defined entity arising in the parotid gland most commonly. Characterized as a low-grade tumor, the majority of patients are diagnosed at an early stage, without regional or distant disease, and the prognosis is relatively good.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1716-1724, 2024.

Efficacy of Fine-Needle Aspiration Cytology in Diagnosing Secretory Carcinoma of Salivary Gland: A Systematic Review and Meta-Analysis

INTRODUCTION

The diagnosis of salivary gland secretory carcinoma (SC) in fine-needle aspiration specimens is challenging because its low-grade nature makes it difficult to differentiate it from various benign or malignant salivary gland neoplasms. Currently, the gold standard is demonstration of ETV6-NTRK3 fusion gene. However, the decision for ordering this costly molecular testing can be facilitated by the correct recognition of its cytomorphological features. The aim of the review was to determine the accuracy of fine-needle aspiration cytology (FNAC) in diagnosis of salivary gland SC. The secondary objective was to recognize varied cytomorphological patterns, characteristic features of SC and differentiate it from other neoplasms.

METHODS

PubMed/MEDLINE, Science Direct, Embase, Cochrane review, and PROSPERO databases were searched for studies having the following key search terms: ("secretory carcinoma of salivary gland" OR "mammary analogue secretory carcinoma of salivary gland") AND ("Cytology" OR "Cytological features" OR "aspirate" OR "cytodiagnosis") published in the time frame of 2010 to June 2023. Studies reporting cytological features of the salivary gland tumors which were confirmed/diagnosed as SC on molecular investigation, were included in the systematic review. Finally, seventeen studies reporting a total of 45 cases were included in the metanalysis.

RESULTS

The sensitivity of the FNAC in diagnosing SC in salivary gland is 27.7% (95% CI: 16.6-42.5%). The LR+ (positive likelihood ratio) was 0.654 (0.344-1.245), LR- (negative likelihood ratio) was 1.023 (0.538-1.946), and diagnostic odds ratio was 0.421 (0.129-1.374). The molecular testing and/or immunohistochemistry performed on cell block increased the diagnostic accuracy.

CONCLUSION

Recognition of subtle cytomorphological patterns, i.e., papillary formation, clusters, and singly dispersed cells along with presence of fine intracytoplasmic vacuolations were the characteristic findings in majority of cases, confirmed with diagnostic molecular profiling. This may be helpful in identification of this rare entity with limited published literature and help in increasing diagnostic accuracy.

NOR-1 (NR4A3) immunostaining on cytologic preparations for the preoperative diagnosis of acinic cell carcinoma of the salivary gland

INTRODUCTION

Acinic cell carcinoma of the salivary gland (ACC-SG) is characterized by recurrent rearrangements in the nuclear receptor subfamily 4 group A member 3 (NR4A3). Immunostaining using an antibody targeting this rearrangement, neuron-derived orphan receptor 1 (NOR-1), has been recently studied on surgical specimens and cell block material of fine-needle aspirates for the diagnosis of ACC-SG. Our goal was to evaluate whether NOR-1 immunostaining could reliably be performed on destained cytologic preparations.

MATERIALS AND METHODS

This was a retrospective multi-institutional study. Immunostaining with the NOR-1 antibody (sc-393902 [H-7], Santa Cruz Biotechnology Inc.) was performed at a titer of 1:30 on destained cytologic preparations. ACC-SG cases (n = 17) were represented by twelve cases with alcohol-fixed preparations (n = 12), including direct smears and SurePath preparations, as well as 5 cases with air-dried preparations (n = 5). These were compared to 27 mimicker lesions (n = 27): normal acini (4), chronic sialadenitis (3), oncocytoma (2), pleomorphic adenoma (6), Warthin tumor (8), mucoepidermoid carcinoma (1), secretory carcinoma (2), and salivary duct carcinoma (1).

RESULTS

The positivity of NOR-1 in ACC-SG cases was 100% on destained alcohol-fixed preparations (12/12) and 60% on air-dried preparations (3/5). All 27 mimicker lesions were negative for NOR-1 (0/27). Evaluation of 2 ACC-SG cases with both types of cytologic preparations showed that NOR-1 was positive on the alcohol-fixed slides but negative on the air-dried slides.

CONCLUSIONS

NOR-1 immunostaining can reliably be performed on alcohol-fixed direct smears and liquid-based preparations for the diagnosis of ACC-SG. Air-dried preparations show a lower positivity rate and may be less suitable for diagnostic immunostaining.