Inflamed benign tumors of the parotid gland: Diagnostic pitfalls from a potentially misleading entity

[Sonography of the neck-aspects of differential diagnosis]

Sonography is the preferred method for primary diagnosis and acute treatment of pathologies involving the neck's soft tissues. Technological advances, particularly high image resolution and multiparametric ultrasound, have improved diagnostic performance. Clinical interest focuses on examining the cervical lymph nodes, salivary glands, and the thyroid gland, as well as space-occupying and inflammatory processes of the neck. In addition, sonography enables targeted minimally invasive histology acquisition using ultrasound-guided biopsies. In this context, the examiner's comprehensive anatomical knowledge and clinical experience are of utmost importance for the quality of findings. This article provides an overview of the most important findings related to sonography of the neck and highlights the relevance of this imaging modality in the hands of the otorhinolaryngologist.

[Primary salivary gland tumors from a pathology perspective : Morphomolecular peculiarities and diagnostic and therapeutic challenges]

Similar to tumors of other organs, salivary gland neoplasms were historically viewed as a single neoplastic entity and mostly treated as such. Accordingly, only the clinical tumor stage, and not the histological subtype, was considered to be of significant prognostic impact. However, over the years, several distinct sub-entities have been characterized based on morphological features, such as adenoid cystic carcinoma, mucoepidermoid carcinoma, acinic cell carcinoma, and salivary duct carcinoma. Most importantly, the nosology of salivary gland carcinomas has undergone a dynamic "splitting" on the basis of morphological, immunophenotypic, and molecular characteristics, so that 21 independent carcinomas are now listed in the current World Health Organization (WHO) classification. Moreover, it has become evident that splitting of these carcinoma subtypes no longer represents a "pathologist's hobby," but carries significant prognostic and therapeutic relevance for optimized cancer surgery and potentially systemic therapy. The current review summarizes the major features of salivary gland tumors, both benign and malignant, and gives an account of their classification systems and genetic profiles.

KRAS codon 12 mutations characterize a subset of de novo proliferating "metaplastic" Warthin tumors

Warthin tumor (WT; synonym: cystadenolymphoma) represents one of the most frequent salivary gland tumors with a frequency equaling or even outnumbering that of pleomorphic adenomas in some series. Histologically, the tumor displays tall columnar oncocytic cells, arranged into two cell-thick layers lining variably cystic glands within an organoid lymphoid stroma. Tumors with exuberant squamous metaplasia in response to FNA-induced or other types of tissue injury/infarction have been referred to as "metaplastic WTs." However, the same terminology was used for tumors with variable mucinous cell and solid or stratified epidermoid proliferations (occasionally mimicking mucoepidermoid carcinoma), although the "metaplasia concept" has never been proven for the latter. We herein investigated 22 WTs showing prominent mucoepidermoid-like or solid oncocytoma-like proliferations without prior FNA or histological evidence of infarction/ trauma using the TruSight Tumor 15 gene panel and KRAS pyrosequencing. As a control, we tested 11 conventional WTs. No statistically significant differences were observed between the two subcohorts regarding patient's age and tumor size. Six of 22 (27%) proliferating/ metaplastic WTs revealed oncogenic KRAS mutations clustering at codon 12 (exon 2), while all conventional tumors lacked these mutations. Our findings are in line with a neoplastic nature of the epidermoid/ mucoepidermoid proliferations in non-injured "metaplastic" Warthin tumors. We propose the descriptive term "de novo proliferating Warthin tumor" for this variant to distinguish it from infarcted/inflamed genuine metaplastic Warthin tumor.

Frozen Section of Parotid Gland Tumours: The Head and Neck Pathologist as a Key Member of the Surgical Team

Introduction: The aim of this study was to evaluate the impact of subspecialised head and neck versus general surgical pathologists on the reliability of the histopathologic evaluation during intraoperative consultation. Materials and Methods: The medical records of all patients who underwent a parotidectomy with frozen section between 2006 and 2021 were retrospectively evaluated. The frozen section was evaluated for sensitivity, specificity, accuracy, and predictive value. Assessment by two groups of pathologists (subspecialised head and neck versus general surgical pathologists) was compared, and the nature or types of misdiagnoses compared with final diagnoses on paraffin sections were analysed for the two groups. Results: Our study sample was made up of 669 cases. The mean age of patients was 57.7 years (range: 10−94 years). Of these, 490 patients had a benign lesion (73.2%), whereas 179 patients had a malignant lesion (26.8%). Frozen section had an overall accuracy of 97.6%, sensitivity for malignancy was 91.1%, specificity was 100%, PPV was 100%, and the NPV was 96.8%. The exact histologic subtype in the group of malignant tumours was correctly identified in FS in 89.4% of cases. A comparison of head and neck pathologists versus general surgical pathologists revealed a highly statistically significant difference concerning both overall detection of malignancy (p < 0.001) as well as correct identification of the histologic subtype (p < 0.001). Conclusion: Involvement of subspecialised head and neck pathologists in the intraoperative consultation for salivary gland tumours results in a gain of 19.8% more sensitivity, underlining the importance of specialisation in salivary gland pathology for the optimisation of frozen section quality.

The Offprint of an Abnormal Pre-Parotidectomy Electrodiagnostic Finding in a Normally Functioning Facial Nerve: Correlation with Intraoperative Findings, Histology and Postoperative Facial Nerve Function

The aim of this study was to search for associations between an electrodiagnostically abnormal but clinically normal facial nerve before parotidectomy and the intraoperative findings, as well as the postoperative facial nerve function. The records of all patients treated for parotid tumors between 2002 and 2021 with a preoperative House–Brackmann score of grade I but an abnormal electrophysiologic finding were studied retrospectively. A total of 285 patients were included in this study, and 222 patients had a benign lesion (77.9%), whereas 63 cases had a malignant tumor (22.1%). Electroneurographic facial nerve involvement was associated with nerve displacement in 185 cases (64.9%) and infiltration in 17 cases (6%). In 83 cases (29.1%), no tumor–nerve interface could be detected intraoperatively. An electroneurographic signal was absent despite supramaximal stimulation in 6/17 cases with nerve infiltration and in 17/268 cases without nerve infiltration (p < 0.001). The electrophysiologic involvement of a normal facial nerve is not pathognomonic for a malignancy (22%), but it presents a rather rare (~6%) sign of a “true” nerve infiltration and could also appear in tumors without any contact with the facial nerve (~29%). Of our cases, two thirds of those with an anatomic nerve preservation and facial palsy had already directly and postoperatively recovered to a major extent in the midterm.

Parotid Warthin's tumor: novel MR imaging score as diagnostic indicator

OBJECTIVES

Despite known characteristic radiologic and clinical features, differentiation between Warthin's tumor (WT) and other parotid tumors remains challenging. The purpose of this study was to more precisely assess the MR imaging features of WT and to develop a scoring system combining the most specific characteristics.

METHODS

A total of 208 patients with parotid gland tumors and presurgical MRI were included. Tumors were divided into 5 histological subtypes, and different MRI features were compared between groups. An MRI scoring test was developed including MR parameters that contributed significantly in distinguishing WT from other tumors.

RESULTS

The best MRI features for differentiating between WTs from other tumors included bilaterality (P = 0.002), multifocality (P < 0.001), ADC values <905.1 (P < 0.001), and high signal intensity on T1-W images (P < 0.001). Six or more points on the 14-point scoring MRI scale was associated with an area under the curve of 0.99 (Accuracy of 98%), while a cut-off value of 7 indicated 100% specificity and 100% positive predictive value.

CONCLUSIONS

Ill-defined margins, low T1-W signal, and location in the upper 2/3 of the parotid gland excluded WTs in 100% of cases. The proposed scoring method allows WTs to be distinguished from other tumors with high accuracy.

KEY POINTS

Application of ultrasound and contrast-enhanced ultrasound to distinguish salivary focal inflammatory masses from malignant masses: A retrospective observational study

BACKGROUND

The aim was to retrospectively analyze the ultrasonographic and clinical characteristics of focal inflammatory masses and malignant masses of salivary gland by using B-mode ultrasound (US) and contrast-enhanced ultrasound (CEUS) for differential analysis.

METHODS

The features of US and CEUS were retrospectively analyzed for 19 cases of focal salivary inflammatory masses and 45 cases of malignant salivary masses. All cases were confirmed by pathohistological examination.

RESULTS

On B-mode US, the incidence of expansive growth patterns of malignant salivary masses (44.4%, 20/45) was significantly higher than that of focal salivary inflammatory masses (15.8%, 3/19) (p = 0.029). The rate of lymphadenopathy surrounding salivary glands of malignant salivary masses (42.2%, 19/45) was significantly higher than that of focal salivary inflammatory masses (15.8%, 3/19) (p = 0.042). On CEUS, clear enhancement margins were more common in malignant salivary masses (44.4%, 20/45) compared to focal salivary inflammatory masses (15.8%, 3/19) (p = 0.029); Rapid washout was more common in malignant salivary masses (82.2%, 37/45) than focal salivary inflammatory masses (31.6%, 6/19) (p <  0.001). Rapid washout on CEUS and craniocaudal diameter were independent predictive factors in differentiating salivary inflammatory masses and malignant masses according to binary logistic regression analysis. US and CEUS achieved a sensitivity of 80.0%, a specificity of 78.9%and an accuracy of 80.0%for discrimination between salivary inflammatory masses and malignant masses.

CONCLUSION

Therefore, a multimodal ultrasonographic pathway combining clinical manifestations, B-mode US and CEUS was needed to differentiate between salivary focal inflammatory masses and malignancies to avoid unnecessary biopsies.

Can Ultrasound in Combination with Virtual Touch Imaging Quantification Predict the Dignity of a Parotid Tumor?

Pre-operative evaluation of a parotid gland tumor is crucial in guiding treatment. This study evaluates the diagnostic performance of B-mode ultrasound in combination with Virtual Touch imaging quantification (VTIQ) in the assessment of parotid lesions. A prospective study of 268 patients with parotid lesions was conducted. Pre-operative ultrasound findings and VTIQ data were compared against histologic results. Ill-defined margins on ultrasound were associated with a significantly higher risk of malignancy (odds ratio [OR] = 1224.0, 95 % confidence interval [CI]: 151.8-9872.7). Faster mean shear waves on VTIQ (OR = 1.81, 95% CI: 1.47-2.23, per 1 m/s increase) and an area with shear wave velocity >6.0 m/s involving >70 % of the lesion (OR = 19.80, 95 % CI: 6.22-63.07) were associated with higher risk of malignancy. Addition of VTIQ to routine pre-operative B-mode ultrasound can provide supplemental information on the dignity of a parotid tumor, allowing for peri-operative procedural optimization.

Conventional, diffusion, and dynamic contrast-enhanced MRI findings for differentiating metaplastic Warthin's tumor of the parotid gland

The purpose of this study was to explore conventional, diffusion, and dynamic contrast-enhanced MRI (DCE-MRI) characteristics for differentiating metaplastic Warthin's tumor (MWT) from other tumor types of the parotid gland, including non-metaplastic Warthin's tumor (non-MWT), pleomorphic adenoma (PA), and malignant tumor (MT). A total of 178 patients with histologically proven tumors of the parotid gland, including 21 MWTs, 49 non-MWTs, 66 PAs, and 42 MTs, were enrolled in the study. Conventional MRI was performed in all patients. One hundred and fifty patients had preoperative diffusion-weighted MR imaging (DWI), and 62 patients had preoperative DCE-MRI. The differences in the conventional, DCE-MRI, and DWI records between MWTs and the other three tumor types were statistically evaluated. Compared with non-MWTs and PAs, there was a statistically significant difference in circumscription (p < 0.01). The ill-defined circumscription was more common in MWTs than non-MWTs and PAs. Compared with PAs, there was a statistically significant difference in morphology (p < 0.05). The lobulated morphology was more common in PAs than MWTs. Compared with PAs and MTs, there was a statistically significant difference in the T2 signal of the solid component (p < 0.01). The T2 moderate intensity of solid components was more common in MWTs than PAs and MTs. The solid components of PAs mostly showed hyperintense on T2-weighted imaging. Cyst/necrosis was more common in MWTs than PAs and MTs. Hyperintense of cyst/necrosis was more common in MWTs and non-MWTs. With respect to contrast enhancement, 52.4% MWTs exhibited moderate or marked enhancement, and most non-MWTs (81.6%) exhibited mild enhancement. Most PAs (84.8%) exhibited marked enhancement. The mean ADC value of MWTs (0.94 × 10-3 ± 0.11 mm2/s) was significantly lower than that of the PAs (1.60 × 10-3 ± 0.17 mm2/s) (p < 0.001). On DCE-MRI, six of eight MWTs demonstrated TIC of type B. Although MWT is rare, conventional MRI characteristics, DWI and DCE-MRI can provide useful information for differentiating MWT from other parotid mass.

Investigation of Sonographic Criteria for Reliable Identification of T1-T2 Low-Grade Malignant Tumors of the Parotid Gland

The aim of this study was to investigate sonographic findings of low-grade malignant tumors of the parotid gland. The sonographic findings of all patients treated for T1-T2 low-grade carcinomas of the parotid gland between 2003 and 2018 were retrospectively examined and compared with those of patients with pleomorphic adenomas for the following parameters: definition of tumor margins, echotexture, echogenicity, shape and vascularization. Statistical analysis was performed using the χ² test. A p value of <0.05 was considered statistically significant. A total of 310 patients (62 with T1-T2 low-grade malignant tumors, 248 with pleomorphic adenomas) were evaluated. Our analysis detected a statistically significant difference in the definition of margins, echotexture, echogenicity and shape. Furthermore, we could detect a specific pattern (anechoic islets in a small hypoechoic lesion with distal enhancement) appearing far more frequently in low-grade malignant lesions. It seems that there is still potential to reduce the incidence of the false working hypothesis "benign lesion" on imaging of low-grade malignant tumors.

Benign parotid mass and facial palsy: systematic review

INTRODUCTION

Parotid masses causing facial palsy are highly indicative of malignancy. A significant number of cases describing benign parotid disease causing facial palsy have been reported.

MATERIALS AND METHODS

We performed a systematic review of the literature to establish the aetiology, clinical features, investigations and management undertaken during these presentations to assess how these factors differed from malignant presentations and to establish an evidence-based algorithm for their management.

RESULTS

A total of 85 cases were identified from 78 articles. Cystadenolymphomas were the most common histopathological type (p = 0.034). Mean facial palsy recovery duration in neoplastic aetiology was longer than for infective aetiology (p = 0.033). A significant association existed between uncommon infective organisms and development of facial palsy (p = <0.0001).

CONCLUSION

Uncommon benign aetiologies are associated with facial palsy. Investigations and management should be guided by patients' clinical presentations, avoiding excessive treatment. Complete facial palsy recovery rates are high, although not immediate.

Primary parotid gland lymphoma: pitfalls in the use of ultrasound imaging by a great pretender

The aim of this study was to highlight several misleading imaging and clinical aspects of parotid gland lymphoma, taking our personal experience and relevant literature reports into consideration. The records of all patients diagnosed with lymphoma in the parotid gland between 2005 and 2017 were examined retrospectively. Sixty-seven patients were included in this study. The mean age was 61.4 years. The most frequent histological entities were marginal zone B-cell lymphoma (31.3%) and follicular lymphoma (28.4%). The tumour was stage I in 35 cases (52.2%), stage II in 13 cases (19.4%), stage III in 11 cases (16.4%), and stage IV in eight cases (11.9%). B symptoms were seen in only three patients (4.5%). The diagnosis was made after parotidectomy in 51 cases (76.1%), by core needle biopsy in 14 cases (20.9%), and by means of open biopsy in the remaining two cases (3.0%). Parotid gland lymphoma represents a diagnostically challenging, multifaceted entity that can easily mimic both benign and malignant conditions. This entity should be included in the differential diagnosis of almost all types of parotid lesion, as it seems to play the role of a great pretender.

Evaluation of preoperative Ultrasonography in the Differentiation between Superficial and Deep Parotid Gland Tumors

Imaging of the intraparotid course of the facial nerve remains a challenge and is not an established routine procedure. The aim of this study was to evaluate ultrasound in localizing a parotid tumor in relation to the facial nerve. The ultrasound findings and operative reports of all patients treated for parotid gland tumors were studied retrospectively. Eight hundred sixty-eight parotid lesions formed our study sample. The unit of measurement was the minimal distance between the parotideomasseteric fascia and the superficial capsule of the tumor, measured in millimeters by means of ultrasound. The mean value for this parameter was 1.3 mm for superficial and 4.6 mm for deep lobe tumors (p < 0.001). When the cutoff value was set at 2.6 mm, the sensitivity and specificity of ultrasound were 89.6 and 88.4%, respectively. Our study revealed that ultrasound can help in the pre-operative differentiation between tumors of the superficial and deep lobes of the parotid gland.

Novel interleukin-33 and its soluble ST2 receptor as potential serum biomarkers in parotid gland tumors

An increasing number of patients with parotid gland tumors have been observed in recent years. The relationship between the immune system and tumor formation is thoroughly investigated. However, newly discovered molecules offer a new insight into the pathophysiology of malignancies. It would be ideal to find an easily determinable biomarker of tumor existence, its malignant potential or a biomarker suggesting the probability of disease recurrence. Our study is the first to examine serum concentrations of IL-33 and its sST2 receptor in patients with various types of parotid gland tumors. Serum IL33, sST2, IL-4 and IL-10 concentrations were determined in patients with benign and malignant parotid gland tumors (pleomorphic adenoma, Warthin's tumor, myoepithelioma and acinic cell carcinoma). We observed for the first time that serum IL-33 level was significantly elevated in patients with various types of parotid gland tumors and sST2 levels were significantly higher in pleomorphic adenoma and acinic cell carcinoma patients compared to the controls. Our results demonstrate for the first time that serum IL-33 and its sST2 receptor may be important factors in the pathology of parotid gland tumors. Although our results are promising, further investigations are required to detect if serum concentrations of those molecules may be a biomarker in parotid gland tumors. Impact statement Parotid gland tumors seem to be an increasingly important medical challenge, mostly due to a noticeable increase in the incidence. It would be crucial to find an easily determinable biomarker of tumor existence, its recurrence or malignant potential. We observed for the first time that serum IL-33 level was significantly elevated in patients with various types of parotid gland tumors and its sST2 receptor levels were significantly higher in pleomorphic adenoma and acinic cell carcinoma patients compared to the controls. We believe that our study helps to understand the biology of the tumors and a potential role of a relatively newly identified cytokine IL-33 in the pathophysiology of the parotid gland tumors.

[Pediatric salivary gland tumors and tumor-like lesions]

Salivary gland tumors and tumor-like lesions in the pediatric population are uncommon. They comprise a heterogeneous group of infectious/inflammatory and neoplastic conditions. Pediatric salivary neoplasms include benign tumors of mesenchymal or epithelial origin as well as malignancies of epithelial (carcinomas), mesenchymal (sarcoma) or hematolymphoid (lymphoma) derivation. Infectious/inflammatory conditions and hematolymphoid malignancies may represent either genuine parenchymal pathology or conditions involving intraglandular lymph nodes of the parotid glands (intraglandular lymphadenopathy and intraglandular nodal lymphomas). Pediatric sialadenitis may be of diverse etiologies including viral (mumps, CMV, HIV, etc.), bacterial, autoimmune (juvenile Sjögren syndrome) or idiopathic (chronic recurrent juvenile sialectatic sialadenitis). Angiomatous lesions (juvenile capillary hemangioma, lymphangioma and vascular malformation) and pleomorphic adenomas represent the most common pediatric benign mesenchymal and benign epithelial tumors, respectively. The vast majority of salivary gland carcinomas in children and adolescents represent low-grade mucoepidermoid carcinomas followed by acinic cell and adenoid cystic carcinomas (together >80% of carcinomas). Other malignant neoplasms include (rhabdomyo-) sarcomas, malignant lymphomas and very rarely sialoblastomas. This long differential diagnosis list of etiologically and biologically highly heterogeneous entities, their shared clinical presentation as "salivary gland enlargement" and the significant differences in their therapeutic strategies and prognosis underline the need for careful assessment to identify the correct diagnosis. Diagnosis is mainly based on a set of typical clinical and imaging features, serological/microbiological findings and, in selected cases, histomorphological characteristics in biopsy specimens.

Contemporary Management of Benign and Malignant Parotid Tumors

To report the standard of care, interesting new findings and controversies about the treatment of parotid tumors. Relevant and actual studies were searched in PubMed and reviewed for diagnostics, treatment and outcome of both benign and malignant tumors. Prospective trials are lacking due to rarity of the disease and high variety of tumor subtypes. The establishment of reliable non-invasive diagnostics tools for the differentiation between benign and malignant tumors is desirable. Prospective studies clarifying the association between different surgical techniques for benign parotid tumors and morbidity are needed. The role of adjuvant or definitive radiotherapy in securing loco-regional control and improving survival in malignant disease is established. Prospective clinical trials addressing the role of chemotherapy/molecular targeted therapy for parotid cancer are needed. An international consensus on the classification of parotid surgery techniques would facilitate the comparison of different trials. Such efforts should lead into a clinical guideline.

Cross-sectional Imaging of Parotid Gland Nodules: A Brief Practical Guide

Clinical evaluation and ultrasound examination are the first steps in the evaluation of a patient with a swelling of the parotid region. After the detection of a nodular lesion, cytological or histological confirmation is usually performed to achieve the diagnosis, while the choice of cross-sectional imaging (computed tomography scan and magnetic resonance imaging) may significantly vary from one physician to another, on the basis of the degree of confidence that both radiologist and surgeon have with this kind of imaging. This work focuses on some essential “reporting points” in cross-sectional imaging evaluation of parotid nodules, chiefly helpful to the radiologist when the ultrasonography assessment is considered incomplete and requires a further evaluation.

Differential diagnosis of parotid gland tumours: which magnetic resonance findings should be taken in account?

Our aim was to define typical magnetic resonance (MRI) findings in malignant and benign parotid tumours. This study is based on retrospective evaluation of pre-surgical MRI of 94 patients with parotid gland tumours. Histology results were available for all tumours. There were 69 cases of benign (73%) and 25 cases of malignant (27%) tumours, including 44 pleomorphic adenomas, 18 Warthin's tumours, 7 various benign tumours, 6 squamous cell carcinomas, 3 carcinoma ex pleomorphic adenomas, 2 mucoepidermoid carcinomas, 1 adenoid cystic carcinoma and 13 various malignant tumours. The following MRI parameters were evaluated: shape, site, size, margins, signal intensity (SI) on T1w and T2w images, contrast enhancement, signal of cystic content, presence or absence of a capsule, perineural spread, extraglandular growth pattern and cervical adenopathy. Statistical analysis was performed to identify the MRI findings most suggestive of malignancy, and to define the most typical MRI pattern of the most common histologies. Ill-defined margins (p < 0.001), adenopathies (p < 0.001) and infiltrative grown pattern (p < 0.001) were significantly predictive of malignancy. Typical findings of pleomorphic adenoma included hyperintensity on T2w images (p = 0.02), strong contrast enhancement (p < 0.001) and lobulated shape (p = 0.04). Typical findings of Warthin's tumour included hyperintense components on T1w images (p < 0.001), location in the parotid inferior process (p < 0.001) and mild or incomplete contrast enhancement (p = 0.01). SI on T1w and T2w images and contrast enhancement enables differential diagnosis between pleomorphic adenoma and Warthin's tumour.

Necrotizing sialometaplasia of the parotid gland associated with facial nerve paralysis

INTRODUCTION

Necrotizing sialometaplasia is a benign inflammatory lesion involving most frequently the minor salivary gland of the hard palate. Involvement of the parotid gland is rare, involvement of the parotid gland associated with facial palsy is exceptional.

CASE REPORT

A 56-year-old male patient with Marfan syndrome presented with swelling and inflammation of the left parotid gland associated with progressively complete facial nerve paralysis. CT scan and MRI showed a parotid collection with hyper signal of the nearest tissues associated with erosion of the styloid process. A malignant tumor was suspected. The histological examination of a biopsy showed a lobulocentric process with necrosis, squamous metaplasia, and inflammation. The immunohistochemical examination supported a final diagnosis of necrotizing sialometaplasia.

DISCUSSION

Necrotizing sialometaplasia of the parotid gland associated with facial nerve paralysis presents like a malignant neoplasm, both clinically and histologically. Only advanced immunohistochemical examination can really confirm the diagnosis.