Differential Diagnosis Of Parotid Tumors Research Articles

Performance of radiomics in the differential diagnosis of parotid tumors: a systematic review.

A systematic review and meta-analysis were conducted to evaluate the diagnostic precision of radiomics in the differential diagnosis of parotid tumors, considering the increasing utilization of radiomics in tumor diagnosis. Although some researchers have attempted to apply radiomics in this context, there is ongoing debate regarding its accuracy. Databases of PubMed, Cochrane, EMBASE, and Web of Science up to May 29, 2024 were systematically searched. The quality of included primary studies was assessed using the Radiomics Quality Score (RQS) checklist. The meta-analysis was performed utilizing a bivariate mixed-effects model. A total of 39 primary studies were incorporated. The machine learning model relying on MRI radiomics for diagnosis malignant tumors of the parotid gland, demonstrated a sensitivity of 0.80 [95% CI: 0.74, 0.86], SROC of 0.89 [95% CI: 0.27-0.99] in the validation set. The machine learning model based on MRI radiomics for diagnosis malignant tumors of the parotid gland, exhibited a sensitivity of 0.83[95% CI: 0.76, 0.88], SROC of 0.89 [95% CI: 0.17-1.00] in the validation set. The models also demonstrated high predictive accuracy for benign lesions. There is great potential for radiomics-based models to improve the accuracy of diagnosing benign and malignant tumors of the parotid gland. To further enhance this potential, future studies should consider implementing standardized radiomics-based features, adopting more robust feature selection methods, and utilizing advanced model development tools. These measures can significantly improve the diagnostic accuracy of artificial intelligence algorithms in distinguishing between benign and malignant tumors of the parotid gland. https://www.crd.york.ac.uk/prospero/, identifier CRD42023434931.

Cavernous hemangioma in adult parotid gland encroaching on the parapharyngeal space: A case report

Hemangiomas account for 0.4-0.6% of all tumors of the parotid gland. With about 50 cases reported worldwide in adults, diagnosing a hemangioma in the parotid gland can be difficult. An accurate diagnosis of parotid hemangiomas in adults before excision is challenging. We report a case of a 54-year-old woman with a left parotid mass of five years duration, which was rapidly increasing in size over last one year. Magnetic resonance imaging (MRI) was suggestive of a left parotid pleomorphic adenoma invading the parapharyngeal space. Fine needle aspiration cytology was inconclusive. However, with a strong clinical suspicion of a pleomorphic adenoma, left total parotidectomy was performed. The histopathological findings were of a cavernous hemangioma. The rarity of such condition in head and neck region and misdiagnosis or failing to diagnose make this case more interesting to pathologists and clinicians alike. Nevertheless, hemangioma should be considered in the differential diagnosis of parotid tumors in adults.

CT-based radiomics with various classifiers for histological differentiation of parotid gland tumors.

This study assessed whether radiomics features could stratify parotid gland tumours accurately based on only noncontrast CT images and validated the best classifier of different radiomics models. In this single-centre study, we retrospectively recruited 249 patients with a diagnosis of pleomorphic adenoma (PA), Warthin tumour (WT), basal cell adenoma (BCA) or malignant parotid gland tumours (MPGTs) from June 2020 to August 2022. Each patient was randomly classified into training and testing cohorts at a ratio of 7:3, and then, pairwise comparisons in different parotid tumour groups were performed. CT images were transferred to 3D-Slicer software and the region of interest was manually drawn for feature extraction. Feature selection methods were performed using the intraclass correlation coefficient, t test and least absolute shrinkage and selection operator. Five common classifiers, namely, random forest (RF), support vector machine (SVM), logistic regression (LR), K-nearest neighbours (KNN) and general Bayesian network (Gnb), were selected to build different radiomics models. The receiver operating characteristic curve, area under the curve (AUC), accuracy, sensitivity, specificity and F-1 score were used to assess the prediction performances of these models. The calibration of the model was calculated by the Hosmer-Lemeshow test. DeLong's test was utilized for comparing the AUCs. The radiomics model based on the RF, SVM, Gnb, LR, LR and RF classifiers obtained the highest AUC in differentiating PA from MPGTs, WT from MPGTs, BCA from MPGTs, PA from WT, PA from BCA, and WT from BCA, respectively. Accordingly, the AUC and the accuracy of the model for each classifier were 0.834 and 0.71, 0.893 and 0.79, 0.844 and 0.79, 0.902 and 0.88, 0.602 and 0.68, and 0.861 and 0.94, respectively. Our study demonstrated that noncontrast CT-based radiomics could stratify refined pathological types of parotid tumours well but could not sufficiently differentiate PA from BCA. Different classifiers had the best diagnostic performance for different parotid tumours. Our study findings add to the current knowledge on the differential diagnosis of parotid tumours.

The Value of Multiparametric Magnetic Resonance Imaging in the Preoperative Differential Diagnosis of Parotid Gland Tumors.

The aim of the present study was to determine the value of multiparametric MRI in the preoperative differential diagnosis of parotid tumors, which is essential for therapeutic strategy selection. A three-year prospective study was conducted with 65 patients. Each patient was investigated preoperatively with multiparametric MRI and surgical excision of the tumor was performed. The preoperative imaging diagnosis was compared with the histopathological report. Several MRI parameters were analyzed, including T1 and T2 weighted image (WI), apparent diffusion coefficient (ADC), time to peak (TTP), and the time intensity curve (TIC). In the differential diagnosis of benign from malignant tumors, T2WI and ADC showed statistically significant differences. Multiparametric MRI had a sensitivity, specificity, and accuracy of 81.8%, 88.6% and 92.3%, respectively. All of the studied parameters (T1, T2, TIC, TTP, ADC) were significantly different in the comparison between pleomorphic adenomas and Warthin tumors. With reference to the scope of this study, the conjunction of multiparametric and conventional MRI demonstrated a sensitivity, specificity, and accuracy of 94.1%, 100%, and 97.8%, respectively. Morphological analysis using conventional MRI combined with diffusion-weighted imaging (DW) and dynamic contrast-enhanced (DCE) multiparametric MRI improved the preoperative differential diagnosis of parotid gland tumors.

A Large Facial Nerve Schwannoma Presenting as a Swelling in Parotid Region-A Rare Case Report.

Extratemporal facial nerve schwannomas are rare entity. Pre-operative assessment is mostly inconclusive with differential diagnosis of parotid tumors. We hereby report a case of 28years female who presented with painless swelling in right parotid region with normal facial nerve function. Ultrasonography was suggestive well circumscribed and homogenous mass arising from the deep lobe of parotid gland. The Fine-needle aspiration cytology came out to be inconclusive. For further characterization of the tumor contrast enhanced MR imaging was performed. The MR imaging revealed well-defined cystic, heterogeneous, pear-shaped mass lesion situated near the stylomastoid foramen. Post operatively the mass came out to be schwannoma on histopathological examination.

Differential diagnostic value of tumor morphology, long/short diameter ratio, and ultrasound gray-scale ratio for 3 parotid neoplasms

The objective of this study was to evaluate the value of tumor morphology, long-to-short diameter ratio (L/S), and ultrasound gray-scale ratio (UGSR) in the differential diagnosis of 3 parotid neoplasms. Preoperative ultrasound images of 17 patients with a malignant tumor (MT), 48 patients with pleomorphic adenoma (PA), and 39 patients with adenolymphoma (AL) were analyzed for imaging features and gray-scale histograms. Tumor morphology, L/S, and UGSR of MT, PA, and AL were compared. Receiver operating characteristic analysis of area under the curve (AUC), sensitivity, and specificity were used to measure the differential diagnostic efficacy of L/S, UGSR, and both combined with tumor morphology. Morphologic features, L/S, and UGSR differed significantly in various pairwise comparisons of the 3 tumor types. Acceptable discrimination was detected between MT and AL with UGSR alone (AUC=0.771) and between PA and AL with L/S and UGSR combined (AUC=0.741). The combination of tumor boundary with UGSR yielded excellent discrimination between MT and PA (AUC=0.853) and between MT and AL (AUC=0.885), with sensitivity and specificity values greater than 0.800. These ultrasound parameters, alone or in combination, can provide a method for accurate presurgical differential diagnosis of parotid tumors.

Histogram analysis of dynamic contrast-enhanced magnetic resonance imaging in the differential diagnosis of parotid tumors

ObjectiveDynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) histograms were used to investigate whether their parameters can distinguish between benign and malignant parotid gland tumors and further differentiate tumor subgroups.Materials and methodsA total of 117 patients (32 malignant and 85 benign) who had undergone DCE-MRI for pretreatment evaluation were retrospectively included. Histogram parameters including mean, median, entropy, skewness, kurtosis and 10th, 90th percentiles were calculated from time to peak (TTP) (s), wash in rate (WIR) (l/s), wash out rate (WOR) (l/s), and maximum relative enhancement (MRE) (%) mono-exponential models. The Mann–Whitney U test was used to compare the differences between the benign and malignant groups. The diagnostic value of each significant parameter was determined on Receiver operating characteristic (ROC) analysis. Multivariate stepwise logistic regression analysis was used to identify the independent predictors of the different tumor groups.ResultsFor both the benign and malignant groups and the comparisons among the subgroups, the parameters of TTP and MRE showed better performance among the various parameters. WOR can be used as an indicator to distinguish Warthin’s tumors from other tumors. Warthin’s tumors showed significantly lower values on 10th MRE and significantly higher values on skewness TTP and 10th WOR, and the combination of 10th MRE, skewness TTP and 10th WOR showed optimal diagnostic performance (AUC, 0.971) and provided 93.12% sensitivity and 96.70% specificity. After Warthin’s tumors were removed from among the benign tumors, malignant parotid tumors showed significantly lower values on the 10th TTP (AUC, 0.847; sensitivity 90.62%; specificity 69.09%; P < 0.05) and higher values on skewness MRE (AUC, 0.777; sensitivity 71.87%; specificity 76.36%; P < 0.05).ConclusionDCE-MRI histogram parameters, especially TTP and MRE parameters, show promise as effective indicators for identifying and classifying parotid tumors. Entropy TTP and kurtosis MRE were found to be independent differentiating variables for malignant parotid gland tumors. The 10th WOR can be used as an indicator to distinguish Warthin’s tumors from other tumors.

Ultrasonography techniques in the preoperative diagnosis of parotid gland tumors - an updated review of the literature.

Preoperative diagnosis of parotid tumors plays a crucial role in selecting and planning the surgical treatment. Ultrasound (US) with its modern techniques can contribute to the differential diagnosis of parotid tumors. This paper aims to achieve a comprehensive review of the ultrasound techniques used in the differential diagnosis of parotid tumors, based on the latest literature data. Considering that most parotid gland tumors are located in the superficial lobe, US is frequently the first imaging technique used for the diagnosis of parotid tumors. Sonoelastography can provide additional data on the elasticity of parotid tumors, but there is an overlap between malignant and benign parotid tumors parameters. Contrast-enhanced ultrasound adds value to conventional ultrasound and allows a more complete characterization of parotid tumors. Many authors have reported promising results using contrast-enhanced ultrasound in the differential diagnosis of parotid tumors. Multiparametric ultrasound with a careful and systematic approach usually allows an accurate differential diagnosis of parotid tumors.

Cross-sectional imaging and cytologic investigations in the preoperative diagnosis of parotid gland tumors - An updated literature review.

An accurate preoperative diagnosis of parotid tumors is essential for the selection and planning of surgical treatment. Various modern cross-sectional imaging and cytologic investigations can support the differential diagnosis of parotid tumors. The aim of this study was to achieve a comprehensive and updated review of modern imaging and cytologic investigations used in parotid tumor diagnosis, based on the latest literature data. This literature review could serve as a guide for clinicians in selecting different types of investigations for the preoperative differential diagnosis of parotid tumors. Magnetic resonance imaging (MRI) with its dynamic and advanced sequences is the first-line imaging investigation used in differentiating parotid tumors. Computed tomography (CT) and positron emission tomography (PET)-CT provide limited indications in differentiating parotid tumors. Fine needle aspiration biopsy and core needle biopsy can contribute with satisfactory results to the cytological diagnosis of parotid tumors. Dynamic MRI with its dynamic contrast-enhanced and diffusion-weighted sequences provides the best accuracy for the preoperative differential diagnosis of parotid tumors. CT allows the best evaluation of bone invasion, being useful when MRI cannot be performed, and PET-CT has value in the follow-up of cancer patients. The dual cytological and imaging approach is the safest method for an accurate differential diagnosis of parotid tumors.

Case report of a large hemangioma of the parotid gland with multiple phleboliths and tonsilloliths

Hemangiomas are benign vascular deformities characterized by an increased proliferation and turnover of endothelial cells. They account for the majority of parotid gland tumors in infants but are rare in adults. Changes in blood flow dynamics within hemangiomas can cause stasis, thrombus formation and phleboliths. Tonsilloliths are calcifications occurring primarily within the palatine tonsillar crypts. We report the case of a large hemangioma of the parotid gland with multiple phleboliths and tonsilloliths in an adult, highlighting the clini cal and imaging features on panoramic radiography, Cone Beam Computed Tomography (CBCT), cervical ultrasound, Magnetic Resonance Imaging (MRI) and Doppler imaging. A 20-year-old woman presented, complaining of a painless swelling below her right ear. Panoramic radiograph showed multiple randomly distributed round-to-oval radiopaque structures overlying the right mandibular ramus. CBCT revealed several radiopaque structures in the right palatine tonsillar crypts. Cervical ultrasound exposed a large heterogeneous and predominantly hypoechogenic mass in the right parotid gland. MRI displayed a well-defined lesion in the right parotid gland extending into the parapharyngeal pre-styloid space, hypointense on T1 and hyperintense on T2, containing several nodules. The diagnosis was: large hemangioma of the right parotid gland extending into the parapharyngeal pre-styloid space, with multiple phleboliths and tonsilloliths. Propranolol was delivered, with periodic follow-up on Doppler images, showing a hemangioma size reduction. Standard radiographs can detect tonsilloliths and phleboliths but additional imaging modalities disclose the exact diagnosis and location of calcifications and the diagnosis, structure and extent of the vascular lesion. Tonsilloliths and phleboliths should be considered in the differential diagnosis of radiopaque masses involving the mandibular ramus. Hemangioma with phleboliths should be considered in the differential diagnosis of parotid tumors when numerous intraglandular calcification nodules are detected on radiographs.

A multiparametric analysis based on DCE-MRI to improve the accuracy of parotid tumor discrimination.

Recently, semiquantitative time-intensity curve (TIC) analysis based on DCE-MRI and apparent diffusion coefficient (ADC) value-based diffusion-weighted imaging (DWI) were used to improve the diagnostic efficiency when diagnosing parotid tumors (PTs). However, quantitative DCE-MRI biomarkers have not been emphasized previously. To explore the diagnostic efficiency of perfusion parameters alone or in combination based on quantitative DCE-MRI and DWI in the differential diagnosis of PTs. In total, 112 patients with parotid masses were prospectively recruited in our hospital from August 2013 to March 2017. All patients were evaluated with DCE-MRI and DWI before surgery. TIC and quantitative parameters based on DCE MRI and ADCs were analyzed. Receiver operating characteristic analysis and linear discriminant analysis (LDA) was used to determine their diagnostic performance. In total, 87% (27/31) of pleomorphic adenoma (PA) showed type A TIC, 74% (65/88) of Warthin's tumors showed type B TIC, and 95% (19/20) of malignant tumors showed TIC type C. Pearson X2 test showed a significant difference between TIC patterns in benign and malignant tumors (X2 = 38.78, p < 0.001). ROC analysis revealed that ADC achieved the best diagnostic performance for distinguishing PA and Warthin's tumor from others, with area under the curve (AUC) values of 0.945 and 0.925 (p < 0.01), respectively. Furthermore, the TIC type was the only useful biomarker for distinguishing malignant from benign PTs, with an AUC of 0.846 (p < 0.01). Concerning the accuracy of the combined application of multiple parameters of DCE-MRI and ADC values, a combination of TIC pattern and extracellular volume ratio (Ve) provided the best results among five protocols, producing the highest accuracy of 0.75, followed by the combined use of the TIC pattern and ADC (accuracy was 0.70). TIC pattern in combination with the Ve biomarker based on DCE-MRI could achieve optimal diagnostic accuracy in the differential diagnosis of PTs.

Diagnostic value of single-source dual-energy spectral computed tomography in differentiating parotid gland tumors: initial results.

An accurate preoperative diagnosis that helps distinguish between benign and malignant parotid gland tumors is very important because the results strongly affect surgical procedures. We aimed to evaluate the value of single-source dual-energy computed tomography (ssDECT) in differentiating malignant from benign parotid gland tumors. Fifty patients underwent enhanced neck ssDECT scanning before surgery. The images were analyzed using the gemstone spectral imaging (GSI) viewer software. Fifty-two tumors (43 patients) were confirmed histopathologically, comprising of 12 pleomorphic adenomas (PAs), 24 Warthin tumors (WTs) (15 patients), and 16 malignant tumors (MTs). The iodine concentration (IC), normalized iodine concentration to common carotid artery (NICA) and slope value of the spectral curve (λHU) of the WTs were significantly higher than those of MTs and PAs (all P<0.05). The optimal IC, NICA and λHU thresholds for differentiating PAs from MTs were 0.91 mg/mL, 0.15 and 1.09, respectively, achieving sensitivities of 91.7%, 91.7% and 91.7%, specificities of 95.0%, 85.0% and 95.0%, and accuracies of 94.2%, 86.5% and 94.2%, respectively for distinguishing PAs from MTs. The optimal IC, NICA and λHU thresholds for distinguishing WTs from MTs were 1.46 mg/mL, 0.20 and 1.72, achieving sensitivities of 91.7%, 95.8% and 91.7%, and specificities of 89.3%, 85.7% and 89.3%, respectively. The accuracy was 90.4%, 90.4% and 90.4%, respectively. The parameters of ssDECT in enhanced CT scans are useful in the differential diagnosis of parotid tumors.

Application of DTI and ARFI imaging in differential diagnosis of parotid tumours.

To explore the utility of diffusion tensor imaging (DTI) and acoustic radiation force impulse (ARFI) imaging in the diagnosis of parotid tumours. 51 patients with parotid tumours were examined with DTI on 3.0-T MRI and ARFI imaging on an ultrasound scanner before surgery. Values of apparent diffusion coefficient (ADC), fractional anisotropy (FA) and shear-wave velocity (SWV) were calculated and analyzed with independent samples Wilcoxon-Mann-Whitney test. Cut-off values, sensitivity and specificity were calculated with receiver-operating characteristic (ROC) curve analysis. The value of combination was calculated through parallel test for the cut-off value of ADC, FA and SWV (combination = 0 or 1); then, ROC analysis was performed with pathological results as the gold standard to calculate the sensitivity and specificity for the combination of the three parameters distinguishing benign and malignant parotid tumours. Pathological diagnosis for every patient was made post-operatively from the tumour tissue taken during operation. There was a significant difference between benign and malignant tumours in the values of ADC, FA and SWV (p = 0.032, p = 0.011 and p < 0.0001); a significant difference in the values was also found between pleomorphic adenoma and malignant tumour (p = 0.0012, p < 0.0001 and p = 0.0002). The diagnosis cut-off points between benign and malignant tumours for ADC, FA and SWV were 1.02 × 10(-3) mm(2) s(-1), 0.24 and 2.76 m s(-1), respectively; the sensitivity for ADC, FA and SWV was 87.50, 62.50 and 68.75%; the specificity was 45.71, 82.86 and 97.14%. Analysis of the combination of the three parameters increased the sensitivity, specificity, Youden index and area under the ROC curve compared with analysis of each parameter alone for distinguishing benign and malignant tumours. The diagnostic value of the combination of the three parameters for distinguishing benign and malignant parotid tumours is the best; SWV is the preferred indicator. Parameters of DTI and ARFI may reflect the histological characteristics of parotid tumours and predict benignancy and malignancy and could provide quantitative information about the tumour. Combination of DTI with ARFI imaging had obvious advantage for the diagnosis of parotid tumours than each alone.

Synchronous Tumors of the Parotid Gland: Presentation of 3 Cases and a Review of the Literature

Synchronous tumors of the parotid gland are two or more neoplasms originating from different sites of the gland, making up less than 1% of all parotid tumors, most frequently as Warthin tumors at more than one site. In this study, 3 cases of synchronous parotid tumors out of 193 parotid surgeries performed between 2004-2010 in our clinic will be presented with their clinical, radiological and histopathological findings, and discussed according to the current literature. The first case was diagnosed as synchronous parotid tumor in composition of pleomorphic adenoma and Warthin tumor. The second case was Warthin tumor at 2 different sites, and the third case was a salivary duct carcinoma with Warthin tumor. Synchronous tumors, despite being rare, are remarkable as they can affect the prognosis and should be kept in mind during the differential diagnosis of parotid tumors.

Is sonoelastography a helpful method for evaluation of parotid tumors?

Sonoelastography is a novel technique, useful in a noninvasive assessment of lesions in multiple organs. The aim of the study was to examine whether the combination of conventional ultrasonography (US) with sonoelastography might improve the reliability of parotid tumor evaluation. Fourty-three consecutive patients with parotid tumors were surgically treated at a single tertiary center at the Department of Otolaryngology, Head and Neck Surgery. The sample included 27 women and 16 men, aged 15–80 (the mean age = 54 years). The reference group constituted of 54 healthy volunteers. High resolution grayscale ultrasonography (US) was performed preoperatively using a 15 MHz linear array transducer. Elastograms (ES) were scored by the conventional Ueno 5-point scale from ES1 (blue-soft) to ES5 (the entire lesion and surrounding area shaded red-stiff). In addition, detailed stiffness values in kPa were collected. The group consisted of 33 patients with benign and 10 patients with malignant tumors. The mean stiffness value was 146.6 kPa in 10 malignant tumors (mostly ES4) and 88.7 kPa in 33 benign tumors (mostly ES2 and ES3). The differences in tissue stiffness between normal parotid parenchyma in the reference group and the mean value for all tumors in the examined group were statistically significant (p < 0.001), and so was the case with the differences between the benign and malignant tumors (p < 0.001). Low stiffness scores (ES1,2) were found in 2 malignant and 15 benign tumors while high scores (ES3,4) were found in 8 malignancies and 18 benign tumors. Sonoelastography overlapping elasticity to the grayscale images supports additional informations. Preferential selection of the lesions characterized by high stiffness (ES4) improves the differential diagnosis of parotid tumors but the large degree of uncertainty of this method should also be pointed out.

Magnetic resonance imaging with pathological correlation in a case of mantle cell lymphoma of the parotid gland: a case report

IntroductionMantle cell lymphoma is a rare non-Hodgkin's lymphoma. It is a subtype of B-cell lymphoma with frequent involvement of the bone marrow and the gastrointestinal tract. Isolated parotid gland involvement seldom occurs. Here we report an unusual case of isolated infiltration of the parotid gland by mantle cell lymphoma. The aim of our study is to correlate magnetic resonance imaging findings with the histological features of the disease. To the best of our knowledge, no similar radiological findings of mantle cell lymphoma have been published before.Case presentationA 72-year-old Caucasian woman presented with a painful left parotid enlargement. She was diagnosed with mantle cell lymphoma involving the left submandibular gland seven years prior to presentation. Her whole body CT scan showed the absence of pathologically enlarged lymph nodes. However, a magnetic resonance imaging showed enlargement of her left parotid gland and an abnormal parenchyma with mixed-type solid and cystic lesions. A biopsy of her left parotid gland and subsequent histological examination confirmed a mantle cell lymphoma (common variant) relapse.ConclusionAlthough rare, the involvement of parotid gland with mantle cell lymphoma must be considered in the differential diagnosis of parotid tumors.

Lipoma of the parotid gland extending from the superficial to the deep lobe: a rarity

Lipoma of the parotid gland is a rare clinical entity. Because of the rarity, they are not often considered in the differential diagnosis of parotid tumors. Lipoma of the parotid gland constitutes around 3% of all parotid tumors. These are asymptomatic and occur both in the deep and the superficial lobe of the parotid. 1 The most favored age group is from the fifth to sixth decade of life and is 10 times more common in the males. 6 Lipoma extending from superficial to deep lobe of parotid gland has not been reported in the literature to our knowledge till date. A 56-year-old male patient, with this relatively rare parotid gland lipoma is reported in this article; it was managed by conservative superficial parotidectomy preserving facial nerve that, if performed correctly, excludes the possibility of any second attack.

Lipoma of the deep lobe of parotid gland - a case report and review of literature.

Lipoma of deep lobe of parotid gland is a rare clinical entity. Less than 10 cases have been reported in the literature in our knowledge. Because of their rarity, they are not often considered in the differential diagnosis of parotid tumors. A case of 45-year-old man with an unusually large deep lobe lipoma of parotid gland is presented in this article which was surgically managed by total conservative parotidectmy. The clinical picture, radiological and histopathological features of this entity is being discussed here. Review of literature of this clinical situation has been presented in the present article.

Value of apparent diffusion coefficient calculation in the differential diagnosis of parotid gland tumors

The differential diagnosis of parotid gland tumors is often difficult with conventional magnetic resonance imaging. To determine whether the calculation of the apparent diffusion coefficient (ADC) is valuable for making the differential diagnosis of parotid tumors. Thirty parotid masses in 28 patients and 24 healthy parotid glands in 12 controls were examined in this prospective study. Diffusion-weighted magnetic resonance imaging with echo-planar spin-echo sequences was used to evaluate each subject. The ADC of each tumor and each healthy parotid gland was calculated. Tumor diagnoses were confirmed by the results of histopathologic analysis. The following types of masses were identified: 11 Warthin tumors, nine pleomorphic adenomas, seven malignant tumors, one basal cell adenoma, and two benign cysts. The mean ADC value for the Warthin tumors was 0.97+/-0.16 x 10(-3) mm(2)/s, for the pleomorphic adenomas was 1.74+/-0.37 x 10(-3) mm(2)/s, for the malignant tumors was 1.04+/-0.35 x 10(-3) mm(2)/s, and for the normal parotid glands was 0.34+/-0.20 x 10(-3) mm(2)/s. The respective ADC value for the single basal cell adenoma was 1.40 x 10(-3) mm(2)/s. Statistically significant differences were identified between the subjects with pleomorphic adenoma and those with another type of parotid tumor, and between subjects with healthy parotid glands and those with a tumor. Calculating the ADC appears to be useful in differentiating pleomorphic adenomas from other types of parotid gland tumors.

Malignant Melanomas of the Parotid

Malignant melanoma (MM) rarely affects the parotid, and usually this diagnosis will herald a search for a primary skin neoplasm. Occasionally, no primary tumor is ever found, raising questions regarding prognosis and the issue of primary melanoma of the parotid. To evaluate retrospectively the clinical and histological features of MM involving the parotid in 19 patients. Pathology and hospital files at 3 tertiary care university hospitals. Patients with MM within the parotid with adequate histopathologic and immunohistochemical documentation, as well as clinical information regarding patient outcome. In 6 patients, no extraparotid MM was ever identified. After parotidectomy, 5 patients (including 1 patient who died of other causes) were melanoma free at a mean of 4.2 years (range, 14 months to 7.5 years). Only 1 patient died of disease after 17 months. An extraparotid primary tumor was present in 13 patients, 10 with dermal and 3 with mucosal sites. At follow-up, only 1 of these patients was disease free after 2 years. Nine patients died of melanoma after a mean of 2.6 years (range, 10 months to 5 years); the other 3 had evidence of metastatic disease at a mean of 4.3 years (range, 3-6 years). Nondermal sites of primary tumors were the nasal cavity, sclera, and conjunctiva. Patients with metastatic MM from unknown primary tumors have a longer disease-free survival than those with metastases from known primary disease. Although rare, MM should be considered in the differential diagnosis of parotid tumors. Unusual mucosal or ocular sites should be considered in the search for possible primary tumor sites to avoid treatment delay. These data support the idea that patients with metastatic MM from unknown primary tumors may follow a more improved course than that of patients with metastases from known primary disease.