3D NLS-Graphy and CT in Pleomorphic Adenoma Diagnosis

Pleomorphic adenoma is one of the most common benign tumors of the major salivary glands. Accurate pleomorphic adenoma diagnosis can sometimes be challenging because the clinical and instrumental signs of salivary gland tumors may be similar. This makes appropriate imaging an important part of the diagnostic process.

This study evaluates the role of 3D NLS-graphy and computed tomography (CT) in the diagnosis of pleomorphic adenomas of the major salivary glands. The study included 143 patients with tumors of the major salivary glands. All patients underwent 3D NLS-graphy, while 64 patients also underwent non-contrast computed tomography. A total of 78 pleomorphic adenomas were identified.

Among the 78 pleomorphic adenomas, 56 cases (71.8%) were located in the parotid salivary glands, while 22 cases (28.2%) were located in the submandibular glands. These findings demonstrate the important role of salivary gland imaging in identifying and characterizing pleomorphic adenomas in different anatomical locations.

The study reported that 3D NLS-graphy demonstrated 100% sensitivity, 96.3% specificity, and 97.7% accuracy in detecting pleomorphic adenomas of the major salivary glands. CT demonstrated sensitivity of 97.6%, specificity of 96.4%, and accuracy of 97.6%.

Introduction to Pleomorphic Adenoma Diagnosis

Space-occupying lesions of the major salivary glands represent an important group of diseases affecting the maxillofacial region. According to the study, the frequency of large space-occupying lesions of the salivary glands in China reached up to 7% of diseases affecting the maxillofacial area.

Pleomorphic adenomas are reported as the most common tumors among space-occupying lesions of the major salivary glands, accounting for approximately 50% to 65.7% according to different studies. Despite their frequency, pleomorphic adenoma diagnosis can present diagnostic difficulties because clinical and instrumental findings may show considerable similarity between different salivary gland lesions.

The reported diagnostic error rate for these lesions varies from 7% to 46%. Therefore, improving imaging techniques and establishing reliable methods for pleomorphic adenoma detection are important objectives in the evaluation of patients with salivary gland tumors.

The main objective of this study was to evaluate and improve the diagnostic approach for pleomorphic adenomas of the major salivary glands using 3D NLS-graphy and non-contrast computed tomography (CT).

Materials and Methods

A total of 143 patients with tumors of the major salivary glands were examined. The patients ranged in age from 15 to 78 years, with a mean age of 48.4 ± 2.5 years. The study population included 103 women and 40 men.

All 143 patients underwent 3D NLS-graphy of the salivary glands, while 64 patients underwent additional CT examination. The 3D NLS-graphy examination was performed according to standard procedures using the Metatron-4025 system with Golden Dragon software and three-dimensional visualization capabilities.

Intratumoral vascularization was evaluated using a six-point Fleindler color scale. 3D NLS-angiography was also used to assess the vascular bed associated with salivary gland lesions. In addition, spectral entropy analysis was performed to assist in evaluating the nature of salivary gland neoplasms.

Non-contrast CT of the major salivary glands was performed using CT scanners in axial projection. The examination used a soft-tissue window to optimize visualization and registration of the salivary glands and surrounding anatomical structures.

Results of Pleomorphic Adenoma Diagnosis

The study identified 78 pleomorphic adenomas. These represented 54.5% of all detected space-occupying lesions of the major salivary glands and 63.4% of all benign tumors of the major salivary glands.

The majority of pleomorphic adenomas were located in the parotid glands. Specifically, 56 cases (71.8%) occurred in the parotid glands, while 22 cases (28.2%) were found in the submandibular glands.

These findings emphasize the importance of detailed salivary gland imaging when evaluating a suspected pleomorphic adenoma. The anatomical location of the tumor can influence its imaging appearance and may also affect the selection of an appropriate diagnostic method.

3D NLS-Graphy Findings in Pleomorphic Adenoma

In 46 cases (82.2%), 3D NLS-graphy demonstrated pleomorphic adenomas of the parotid salivary gland as oval or round hyperchromogenic formations with distinct contours and a heterogeneous structure.

The surrounding salivary gland parenchyma generally did not show significant changes in structure or chromogeneity. Pleomorphic adenomas measuring up to 1 cm demonstrated a homogeneous chromogenic structure, whereas adenomas larger than 1 cm demonstrated a homogeneous isochromogenic structure associated with areas of hemorrhage and discharge.

Pleomorphic adenomas of the submandibular glands were characterized by hyperchromogenic foci with different shapes. These imaging characteristics contributed to the overall assessment of pleomorphic adenoma diagnosis using 3D NLS-graphy.

The study also found that 3D NLS-angiography demonstrated vascular bed involvement in 74 cases, corresponding to 94.9% of pleomorphic adenoma cases. Spectral entropy analysis was additionally used to differentiate pleomorphic adenomas from other benign salivary gland tumors, including leiomyoma, teratoma, and neurinoma.

CT Findings in Pleomorphic Adenoma

Computed tomography provided additional information for pleomorphic adenoma diagnosis, particularly in relation to tumor density, size, contours, and anatomical extension.

In 44 cases (93.6%), CT demonstrated pleomorphic tumors of the parotid gland as single high-density formations with a round shape, distinct edges, and smooth contours. The average density was 29.6 ± 4.2 HU.

The tumor structure was heterogeneous in 25 cases (53.2%) and homogeneous in 22 cases (46.8%). The average tumor size was 2.9 ± 0.9 cm, while tumors located in the deep lobe of the gland reached sizes of up to 5.1 cm.

In a small number of patients, the tumor density was similar to that of the surrounding salivary gland parenchyma. This finding could make CT diagnosis of pleomorphic adenoma more difficult, particularly when tumors were located in narrow portions of the salivary gland.

Pleomorphic adenomas of the submandibular glands demonstrated somewhat different imaging characteristics. Unlike many parotid gland lesions, they did not always have clearly defined boundaries separating the tumor from the gland. Their density could correspond to the surrounding parenchyma, and the average tumor size was 3.6 ± 1.3 cm.

Significant enlargement of the affected gland compared with the opposite side and displacement of surrounding soft tissues were also observed in these cases.

Comparison of 3D NLS-Graphy and CT

The findings of the study demonstrate that both 3D NLS-graphy and CT can provide valuable information for the evaluation of pleomorphic adenomas of the major salivary glands.

Previous descriptions of pleomorphic adenomas using NLS methods commonly characterize these lesions as round, hyperchromogenic formations, generally corresponding to 5–6 points on the Fleindler scale. The surrounding salivary gland parenchyma was usually structurally and chromogenically unchanged.

According to the study data, pleomorphic adenomas of the submandibular glands differed from parotid gland tumors by demonstrating isochromogenic foci with different forms and high chromogeneity. The preserved salivary gland parenchyma was visualized more clearly with NLS-graphy compared with CT.

CT showed a homogeneous pattern in 75% of cases, while clear and well-defined tumor edges were identified in approximately 90% of pleomorphic adenomas. These findings were consistent with previously reported literature data.

Role of 3D NLS-Graphy in Salivary Gland Imaging

The study suggests that 3D NLS-graphy can play an important role in the preliminary evaluation of salivary gland neoplasms. Its ability to provide three-dimensional visualization, assess tumor structure and chromogeneity, and perform spectral entropy analysis makes it useful for the initial assessment of suspected pleomorphic adenoma.

The results showed that NLS-graphy provided particularly high sensitivity for detecting pleomorphic adenomas. Therefore, the authors considered 3D NLS-graphy a leading visualization method for the initial assessment of space-occupying lesions of the major salivary glands.

However, CT remained important in specific clinical situations. According to the study, CT was particularly useful for evaluating deep-seated tumors, determining the three-dimensional extent of a lesion, and assessing the relationship between the tumor and the facial nerve.

This anatomical information can be important when determining subsequent treatment strategies. CT was also recommended when a malignant process was suspected or when the tumor involved the deep lobe of the gland.

CT for Large or Deep-Seated Salivary Gland Tumors

Tumor size is another important factor in selecting an appropriate imaging method. The study indicates that when a salivary gland formation is larger than 3 cm in diameter, regardless of its nature or location, CT should be performed to obtain accurate information about the extent of the tumor and its relationship with surrounding tissues.

This is particularly important for tumors that extend into deeper anatomical spaces. CT can provide detailed information about tumor volume, structure, and adjacent anatomical structures, which may be essential for treatment planning.

For non-glandular formations, particularly lesions located in the peripharyngeal space, intravenous enhancement during CT may also be useful for determining the relationship of the mass to major vascular structures such as the carotid artery and jugular vein.

Diagnostic Accuracy of 3D NLS-Graphy and CT

One of the most important findings of the study concerns the diagnostic performance of the two imaging methods.

For pleomorphic adenoma detection, 3D NLS-graphy demonstrated:

• Sensitivity: 100%
• Specificity: 96.3%
• Accuracy: 97.7%

CT demonstrated:

• Sensitivity: 97.6%
• Specificity: 96.4%
• Accuracy: 97.6%

These results indicate that both imaging methods demonstrated high diagnostic performance in the study. 3D NLS-graphy showed particularly high sensitivity, while CT provided important additional anatomical information, especially for larger and deep-seated tumors.

Conclusion

The analysis of patients with space-occupying lesions of the major salivary glands demonstrated that 3D NLS-graphy can serve as an important visualization method in pleomorphic adenoma diagnosis.

3D NLS-graphy allows assessment of tumor size, structure, shape, chromogeneity, and tumor type with the additional use of spectral entropy analysis. The study reported high sensitivity, specificity, and overall accuracy for 3D NLS-graphy in detecting pleomorphic adenomas of the major salivary glands.

At the same time, computed tomography (CT) remains valuable when evaluating tumors larger than 3 cm, deep-seated lesions, or tumors where accurate assessment of the surrounding anatomical structures is required.

Overall, the study concludes that 3D NLS-graphy and CT have complementary roles in the imaging evaluation of salivary gland tumors. 3D NLS-graphy may be sufficient for preliminary assessment in many cases, while CT can provide more detailed information about tumor extension, volume, deep anatomical involvement, and adjacent structures when clinically indicated.