Two case reports of synchronous unilateral pleomorphic adenoma and cystadenolymphoma of the parotid gland with literature review

In the first case, a 71-year-old female tobacco smoker consulted a physician due to a slowly growing tumor of the right parotid gland she noticed several years earlier. The tumor was palpated preauricularly in the right Regio parotidea. In the physical examination, the facial nerve was intact on both sides.

Sonographically, the first tumor was well-defined, hypoechoic with an anechoic zone and located in the caudal parotid pole. It measured 13.8 × 15.3 × 21.0 mm (Fig. 3). VTIQ showed an elastic tumor (color-rated: blue to green, Fig. 2). This technology utilizes an acoustic push pulse to examine the displacement of tissue elements. This information is used to create a qualitative map. Blue regions depict tissue that is less stiff than red colored regions (Fig. 1, Fig. 2). The second tumor was located over the musculus masseter and measured 32.2 × 15.2 × 31.0 mm. It was well-defined as well, but lobulated. It showed an anechoic area, echogenic internal echoes and distal acoustic enhancement (Fig. 4, Fig. 5). It was diffusely vascularized (Fig. 6). In the VTIQ, the tissue was also less stiff with a “black hole” representing a cystic area (Fig. 2). Due to the different appearance of the two lesions in preoperative ultrasound, the presence of two distinct entities was suspected. Therefore, a decision to perform a complete parotidectomy without prior fine needle aspiration was made. The two lesions were removed and sent for histological examination. The macroscopic differences on the cut surfaces were clearly visible (Fig. 7).

Fig. 3.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

On histopathologic examination, the mass with polycystic areas turned out to be a cystadenolymphoma, whereas the other tumor was diagnosed as a pleomorphic adenoma.

The second case was a 68-year-old woman with two masses in the right parotid gland. On physical examination, two indolent tumors were palpable. Sonographically, two welldefined masses were seen, one preauricular and one in the caudal pole of the right parotid gland. The preauricular, hypoechoic, homogeneous tumor measured 11.5 × 5.6 × 8.2 mm and showed distal acoustic enhancement (Fig. 8). The one in the caudal pole, also hypoechoic and with distal acoustic enhancement, but with echogenic internal echoes, measured 18.9 × 10.2 × 11.8 mm (Fig. 9). Its vascularization was rather peripheral (Fig. 10). Histologically, a pleomorphic adenoma and a cystadenolymphoma were diagnosed as well.

Fig. 8.

Fig. 9.

Fig. 10.

Multiple salivary gland tumors account for about 5–10% of parotid gland lesions with Warthin tumors being the most common. As mentioned before, synchronous parotid tumors with different histological types account for less than 1% of all salivary gland tumors and the most common combination is Warthin tumor with pleomorphic adenoma⁽⁶⁾. A few cases of synchronous benign and malignant tumors are reported but they are extremely rare. In these cases, the most common combination is Warthin tumor and mucoepidermoid carcinoma⁽³⁾.

Preoperative imaging is of great importance. Diagnostic accuracy rates of approximately 90% can be achieved. Sonography is the first choice imaging to differentiate between tumor types⁽¹⁾. Further imaging modalities, predominately MRI, can be used when the tumor is large and sonographically difficult to assess in its extent. Ultrasound and MRI seem to be very efficient in differentiating between benign and malignant lesions⁽⁷⁾. In a study of Mansour et al. ⁽⁸⁾, 202 patients with parotid gland lesions were examined with the use of multimodal ultrasonographic pathway including high-resolution B-mode ultrasound, real-time sonoelastography, color-coded duplex sonography and contrast-enhanced ultrasound.

They concluded that B-mode ultrasound in combination with clinical examination and medical history is able to identify malignant tumors with a sensitivity of up to 77% and with a specificity of up to 98%. The authors suggested that this is a useful method to predict the dignity of tumors, to plan the required surgery and to prevent re-operations⁽⁵⁾.

Elastography is a useful additional modality to provide further qualitative and quantitative information about tissue stiffness and to evaluate the dignity⁽⁹⁾. VTIQ is a new technology of two-dimensional shear wave imaging, which provides a combination of quantitative and relative stiffness imaging. In general, malignant tissue is stiff and benign tissue is soft. Pleomorphic adenoma seems to be stiffer than cystadenolymphoma but less stiff than malignant tumors⁽¹⁾.

Preoperative Fine-needle aspiration cytology (FNAC) guided by ultrasound is widely used because it is fast and provides additional information about the tumor’s dignity, helping with better treatment planning. Core needle biopsy on the other hand is controversially discussed due to the possible tumor seedling and the risk of fistula formation^(1,10).

Complete resection of the tumor with lateral or total parotidectomy is the gold standard⁽⁶⁾. Depending on the dignity of the tumor, an adjuvant therapy may be necessary.

The vast majority of multiple salivary gland tumors are cystadenolymphomas, also known as Warthin’s tumors. However, clinicians should be aware of the possible coexistence of tumors of different histological types in ipsilateral salivary glands. B-mode ultrasound in combination with color-coded duplex sonography and VTIQ may improve the accuracy of preoperative diagnosis. Ultrasound is the most important modality to predict the dignity and to plan required surgery.