Mucosa-associated lymphoid tissue lymphoma of the salivary glands: MR imaging findings including diffusion-weighted imaging

Current status of diffusion-weighted imaging in differentiating parotid tumors

Recently, diffusion-weighted imaging (DWI) is an essential magnetic resonance imaging (MRI) protocol for head and neck imaging in clinical practice as it plays an important role in lesion detection, tumor extension evaluation, differential diagnosis, therapeutic effect prediction, therapy evaluation, and recurrence diagnosis. Especially in the parotid gland, several studies have already attempted to achieve accurate differentiation between benign and malignant tumors using DWI. A conventional single-shot echo-planar-based DWI is widely used for head and neck imaging, whereas advanced DWI sequences, such as intravoxel incoherent motion, diffusion kurtosis imaging, periodically rotated overlapping parallel lines with enhanced reconstruction, and readout-segmented echo-planar imaging (readout segmentation of long variable echo-trains), have been used to characterize parotid tumors. The mean apparent diffusion coefficient values are easily measured and useful for assessing cellularity and histological characteristics, whereas advanced image analyses, such as histogram analysis, texture analysis, and machine and deep learning, have been rapidly developed. Furthermore, a combination of DWI and other MRI protocols has reportedly improved the diagnostic accuracy of parotid tumors. This review article summarizes the current state of DWI in differentiating parotid tumors.

Radiomic Features Associated with Lymphoma Development in the Parotid Glands of Patients with Primary Sjögren's Syndrome

Non-Hodgkin Lymphoma (NHL) represents a severe complication and the main cause of morbidity in patients with primary Sjögren's syndrome (pSS). This study aimed to assess the role of textural analysis (TA) in revealing lymphoma-associated imaging parameters in the parotid gland (PG) parenchyma of patients with pSS. This retrospective study included a total of 36 patients (54.93 ± 13.34 years old; 91.6% females) diagnosed with pSS according to the American College of Rheumatology and the European League Against Rheumatism criteria (24 subjects with pSS and no lymphomatous proliferation; 12 subjects with pSS and NHL development in the PG, confirmed by the histopathological analysis). All subjects underwent MR scanning between January 2018 and October 2022. The coronal STIR PROPELLER sequence was employed to segment PG and perform TA using the MaZda5 software. A total of 65 PGs underwent segmentation and texture feature extraction (48 PGs were included in the pSS control group, and 17 PGs were included in the pSS NHL group). Following parameter reduction techniques, univariate analysis, multivariate regression, and receiver operating characteristics (ROC) analysis, the following TA parameters proved to be independently associated with NHL development in pSS: CH4S6_Sum_Variance and CV4S6_Inverse_Difference_Moment, with an area under ROC of 0.800 and 0.875, respectively. The radiomic model (resulting by combining the two previously independent TA features), presented 94.12% sensitivity and 85.42% specificity in differentiating between the two studied groups, reaching the highest area under ROC of 0.931 for the chosen cutoff value of 1.556. This study suggests the potential role of radiomics in revealing new imaging biomarkers that might serve as useful predictors for lymphoma development in patients with pSS. Further research on multicentric cohorts is warranted to confirm the obtained results and the added benefit of TA in risk stratification for patients with pSS.

MR Imaging of Salivary Gland Tumors

Neoplasms of the salivary glands are characterized by their marked histologic diversity giving them nonspecific imaging findings. MR imaging is the best imaging modality to evaluate salivary gland tumors. Multiparametric MR imaging combines conventional imaging features, diffusion-weighted imaging, and perfusion imaging to help distinguish benign and low-grade neoplasms from malignant tumors; however, a biopsy is often needed to establish a definitive histopathologic diagnosis. An awareness of potential imaging pitfalls is important to prevent mistakes in salivary neoplasm imaging.

A Primary Parotid Mucosa-Associated Lymphoid Tissue Non-Hodgkin Lymphoma in a Patient With Sjogren Syndrome

The salivary gland tumors are rare entities and the majority of these are benign. However, there are some entities such as prior neck radiation, certain infections, and systemic diseases which should raise the clinical suspicion for a malignant lesion. Patients with Sjogren syndrome are at increased risk for a salivary gland neoplasm, specifically non-Hodgkin lymphoma. While clinical findings play an important role in the initial workup, imaging plays a critical role in the diagnosis and management. This case describes a patient with Sjogren syndrome who presented with a left face mass where imaging was able to confidently diagnose her with a suspicious parotid neoplasm with lymphoma as the favored diagnosis. After histological evaluation, she was diagnosed with primary parotid mucosa-associated lymphoid tissue (MALT) non-Hodgkin lymphoma after which she went on to non-operative management.

Imaging of head and neck mucosa-associated lymphoid tissue lymphoma (MALToma)

Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALToma) arises in extranodal sites in the head and neck. Chronic inflammatory, infectious or autoimmune conditions are implicated in its pathogenesis. Within the head and neck, MALToma is often multifocal and indolent and the imaging appearances may be mistaken for non-malignant disease in the head and neck. The aim of this article is to illustrate the varied radiological and clinical features of MALToma in the head and neck, an awareness of which is needed for timely and correct diagnosis to guide subsequent disease management.

Radiogenomics and Its Role in Lymphoma

PURPOSE OF REVIEW

Imaging features of lymphoma vary regionally. Awareness of site-specific key imaging characteristics of lymphoma can aid in rapid staging and assist in prompt treatment. FDG PET/CT and conventional MRI are readily available diagnostic modalities with excellent sensitivity and good specificity. Diagnostic specificity can be enhanced using emerging PET radiotracers, e.g., FLT and FET.

RECENT FINDINGS

Emerging research has shown higher dimensional analysis (radiomics and radiogenomics) of imaging data can yield information of the underlying genetic aberrations in lymphoma, which can aid in assessing real-time evolution of tumor. CT, PET/CT, MRI, and ultrasound accentuate the intrinsic qualities of lymphoma (e.g., FDG PET/CT for increased metabolic activity, FLT PET/CT for increased proliferation index, and DWI for increased cellularity) and play an essential role in its diagnosis and examination. Advanced radiogenomic analyses use radiomic parameters to deduce genetic variations of lymphoma, providing noninvasive, repeatable, and real-time surveillance of its genetic progression.

Current status of imaging of Sjogren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease, which involves salivary glands (SG) and extra glandular organs. Today, Sjögren's patients' diagnosis is based on classification criteria taking into account five objective tests, including histology, immunology, two ophthalmological tests, and salivary flow evaluation. To date, the challenge is to find the right imaging tool for diagnosis, follow up, and prognosis of pSS. The objective of this review is to describe as to what are these imaging modalities and particularly the place and validity of salivary glands ultrasonography (SGUS) in the diagnosis and follow-up strategy of patients with suspected pSS. Moreover, new noninvasive tools are emerging, including elastography, a new ultrasonography technique that provides an estimate of tissue elasticity, MRI, MR sialography, and ¹⁸ fluorodeoxyglucose-positron emission tomography. Although new imaging opportunities are available, SGUS should be the first-line choice in pSS because of its accessibility, feasibility over time, and sensitivity to change.

Multiparametric magnetic resonance imaging of parotid tumors: A systematic review

PURPOSE

The purpose of this systematic review was to provide an overview of the contribution of multiparametric magnetic resonance imaging (MRI) in the diagnosis of parotid tumors (PT) and recommendations based on current evidences.

MATERIAL AND METHODS

We performed a retrospective systematic search of PubMed, EMBASE, and Cochrane Library databases from inception to January 2020, using the keywords "magnetic resonance imaging" and "salivary gland neoplasms".

RESULTS

The initial search returned 2345 references and 90 were deemed relevant for this study. A total of 54 studies (60%) reported the use of diffusion-weighted imaging (DWI) and 28 studies (31%) the use of dynamic contrast-enhanced (DCE) imaging. Specific morphologic signs of frequent benign PT and suggestive signs of malignancy on conventional sequences were reported in 37 studies (41%). DWI showed significant differences in apparent diffusion coefficient (ADC) values between benign and malignant PT, and especially between pleomorphic adenomas and malignant PT, with cut-off ADC values between 1.267×10^-3mm²/s and 1.60×10^-3mm²/s. Perfusion curves obtained with DCE imaging allowed differentiating among pleomorphic adenomas, Warthin's tumors, malignant PT and cystic lesions. The combination of morphological MRI sequences, DCE imaging and DWI helped increase the diagnostic accuracy of MRI.

CONCLUSION

Multiparametric MRI, including morphological MRI sequences, DWI and DCE imaging, is the imaging modality of choice for the characterization of focal PT and provides features that are highly suggestive of a specific diagnosis.

Sjögren Syndrome in Primary Salivary Gland Lymphoma

OBJECTIVES

Sjögren syndrome (SS) is considered as a major etiologic factor for primary salivary gland lymphoma (SGL). However, the percentage of SGL that is caused by SS (and thus the real impact of SS on SGL epidemiology) is unclear. We aimed to assess the prevalence of SS in patients with SGL through a systematic review and meta-analysis.

METHODS

Electronic databases were searched for studies assessing the presence of SS in patients with SGL. Pooled prevalence of SS in SGL was calculated, with a subgroup analysis based on histotype (mucosa-associated lymphoid tissue [MALT] vs non-MALT).

RESULTS

Sixteen studies with 665 SGLs were included. Pooled prevalence of SS in SGL was 18.2%, with high heterogeneity among studies. In MALT SGL, the prevalence of SS was 29.5%, with moderate heterogeneity. In non-MALT SGL, the prevalence of SS was 0%, with null heterogeneity.

CONCLUSIONS

SS seems to be responsible for a significant but minor portion of SGLs. SS appears involved in MALT-type SGL but not in other histotypes.

Case report of API2-MALT1 fusion-positive MALT lymphoma arising from bilateral submandibular glands with no evidence of autoimmune syndromes

Mucosa-associated lymphoid tissue (MALT) lymphoma arising from the salivary glands is usually associated with chronic infection or autoimmune syndromes, such as primary Sjogren syndrome. The occurrence of t(11;18)/API2-MALT1 is rare in salivary MALT lymphoma. Here we describe a case of API2-MALT1 fusion-positive MALT lymphoma of the bilateral submandibular glands with no evidence of autoimmune syndromes. A 70-year-old man complained of a painless swelling in the bilateral submandibular gland. Serology examination results were negative for anti-SSA and anti-SSB. His right submandibular gland was dissected, and he was diagnosed with MALT lymphoma with the API2-MALT1 fusion gene. Positron emission tomography/computed tomography scanning indicated mild fluorine-18-fluorodeoxyglucose uptake in the left submandibular gland and liver. He was treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone. After 6 years, the patient is alive and disease free. In the present case, the patient with API2-MALT1 fusion-positive MALT lymphoma had a good outcome despite the advanced clinical stage.

A comparison of conventional and diffusion-weighted magnetic resonance imaging in the diagnosis of sialadenitis and pleomorphic adenoma

OBJECTIVES

The aim of this study was to compare the efficacy of conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) in correctly identifying the presence of disease in the major salivary glands and correctly distinguish sialadenitis from pleomorphic adenoma.

STUDY DESIGN

Twenty-one patients diagnosed with unilateral sialadenitis or pleomorphic adenoma were selected. The nonaffected contralateral glands were also analyzed. T1- and T2-weighted MRI and DWI were obtained using spin-echo pulse sequences with a 1.5 Tesla MRI device. The diagnostic performance of 3 observers was evaluated for detection of salivary gland alterations and differentiation between sialadenitis and pleomorphic adenoma based on evaluation of MRI in comparison with DWI.

RESULTS

Intra-and interobserver reliability ranged from 0.86 to 0.94. DWI demonstrated greater sensitivity and accuracy values compared with MRI for both detection of disease and differentiation of sialadenitis from pleomorphic adenoma, with specificity values that were greater than or equal to those of MRI. DWI yielded significantly higher diagnostic odds ratios compared with MRI for both identification of disease and differentiation between lesions.

CONCLUSIONS

DWI demonstrated better diagnostic performance in the detection of alterations in the salivary glands and in differentiating between sialadenitis and pleomorphic adenoma compared with conventional T1 and T2-weighted MRI.

Routine and Advanced Diffusion Imaging Modules of the Salivary Glands

This article reviews the role of routine and advanced diffusion imaging modules of the salivary glands. Routine and advanced diffusion imaging modules have a role in differentiation of malignant from benign salivary gland tumors, characterization of some benign salivary gland tumors, and staging of salivary gland cancer. The role of advanced diffusion modules in patients with salivary gland cancer after surgery, radiation therapy, or radioiodine therapy is discussed. Advanced diffusion imaging modules can help in diagnosis and staging of Sjögren syndrome.

Imaging of the sublingual and submandibular spaces

Abstract

Divided by the mylohyoid muscle, the sublingual and submandibular spaces represent a relatively small part of the oral cavity, but account for a disproportionate amount of pathological processes. These entities are traditionally separated into congenital, infectious/inflammatory, vascular and neoplastic aetiologies. This article reviews the relevant anatomy, clinical highlights and distinguishing imaging features necessary for accurate characterisation.

Teaching Points

• The mylohyoid sling is a key anatomical landmark useful in surgical planning.

• Congenital lesions and infectious/inflammatory processes constitute the majority of pathology.

• Depth of invasion is key when staging tumours in the oral cavity.

Diffusion-weighted MRI for differentiation between sialadenitis and pleomorphic adenoma

OBJECTIVES

The aim of this study was to compare apparent diffusion coefficient (ADC) values from diffusion-weighted MRI (DWI) among normal salivary glands, cases with sialadenitis and cases with pleomorphic adenoma of major salivary glands.

METHODS

22 patients (totalling 44 major salivary glands) diagnosed with either unilateral sialadenitis (on either parotid or submandibular gland) or parotid gland pleomorphic adenoma were selected. Contralateral non-affected glands (normal) were also analyzed. DW images were achieved using a spin-echo pulse sequence with a 1.5-T MRI device. Mean ADC values were compared among the three groups analyzed (contralateral normal glands, sialadenitis and pleomorphic adenoma).

RESULTS

The mean ADC values were significantly higher in cases of parotid sialadenitis (p = 0.001), but not in cases of submandibular sialadenitis (p = 0.466), as compared with the contralateral non-affected glands. Cases of pleomorphic adenoma presented the highest ADC values of the study. In addition, one-way ANOVA test revealed a significant difference among the three groups of parotid glands analyzed.

CONCLUSIONS

Within the limitations of this study, the present results suggest that DWI allows for differentiation between parotid sialadenitis and pleomorphic adenoma.

Clinical features and management of non-gastrointestinal non-ocular extranodal mucosa associated lymphoid tissue (ENMALT) marginal zone lymphomas

Extranodal mucosa associated lymphoid tissue (ENMALT) marginal zone lymphomas may arise at any site of the body. The most frequent localizations other than gastrointestinal and eye are salivary gland, skin, lung and thyroid. These lymphomas usually arise in a setting of inflammation due to a persistent infection or autoimmune diseases such as Sjogren syndrome in salivary MALT lymphomas and Hashimoto's thryroiditis in thyroid lymphomas. They affect middle-aged patients with a female predominance when lymphoma arises in certain locations. Patients often present with localised stage I or II although disseminated disease may be present at diagnosis or relapse in a third of the cases. Biopsy of the affected site is mandatory to establish the diagnosis and a full work-up staging is recommended. The clinical course is indolent and prognosis is good despite that recurrences following response to therapy are frequent. Surgery, radiotherapy and/or Rituximab based regimens are effective in these lymphomas.

Extranodal Marginal Zone Lymphoma of the Parotid Gland

Non Hodgkin lymphomas correspond to 25 % of all head and neck cancers. These rare tumors only include less than 5 % of malign tumors in parotid region. Differential diagnosis of these tumors cover many malign and benign tumors of the parotid gland. Definite diagnosis depends on sufficient tissue material of parotidectomy specimen. Treatment modality is surgical removal of the lesion with or without additional radiation and chemotherapy depending on the stage of the tumor. Prognosis is better than other forms of the B-cell lymphoma. We present a 54 year old woman who suffered from progressively and slowly growing mass on parotid region, without any inflammatory disease or chronic infection, diagnosed with mucosa associated lymphoid tissue lymphoma of the parotid gland. Parotid gland was totally excised by superficial parotidectomy and there is no recurrence after 5 years postoperative period.

[A Clinical Study of a Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma of Salivary Glands]

Malignant lymphoma involving the salivary glands is a rare entity that accounts for only 1 to 4% of all salivary gland tumors. We have analyzed the clinical features of MALT lymphoma of the salivary glands in 7 patients whom we have treated in the past 10 years, including data from 43 patients in the literature. The most common symptom was persistent or progressive swelling of the salivary glands without pain or facial palsy. The affected glands were the unilateral parotid in 62%, the unilateral submandibular gland in 6.8%, and the bilateral parotid or submandibular gland in 6.8%. The salivary gland swelling as evaluated by MRI or ultrasonography consisted of a localized solitary tumor in 68.9%, multiple tumors in 10.3%, and diffuse swelling of the gland in 26.1%. In 24 out of 50 patients, MALT lymphoma developed on the basis of Sjögren's syndrome. As for diagnosis, malignant lymphoma was suspected only in 4 cases out of 11 (36.7%) based on the fine needle aspiration cytology. In all patients, a definitive diagnosis was obtained based on histopathological study of the localized tumor or the biopsy specimens. When patients with Sjögren's syndrome have developed persistent swelling of the salivary glands, it is necessary to rule out malignant lymphomas, especially MALT lymphoma, by combination of ultrasonography, MRI, FNA, and biopsy or open surgery depending on image findings. The treatment of MALT lymphoma has not yet been standardized because MALT lymphoma is a rare entity. The choice of initial treatment is important because it is related to its prognosis. If MALT lymphoma remains in a local site, we should undertake an operation or radiotherapy. If MALT lymphoma has dissemineated systemically, we should choose chemotherapy.