The team of the Department of Imaging Diagnostics of the University Hospital “St. Catherine“ made a contribution to science and medicine with the publication of an extremely rare salivary gland tumor in one of the most renowned international journals Oral Radiology. Dr. Niya Slavkova Bakic from the Department of Imaging Diagnostics of the University Hospital “Saint Catherine“ spoke to FACTS on the subject.
- Dr. Bakic, what is the parotid gland and why is it so important from an anatomical and functional point of view?
- The parotid gland (glandula parotis) is the largest salivary gland and is located in the parotid (retromandibular) region, lateral to the shoulder of the lower jaw and anteroinferior to the external auditory canal. It covers the space between m. masseter and m. sternocleidomastoideus. It has a complex anatomical organization, with the facial nerve passing through its parenchyma, which divides it into superficial and deep lobes, as well as important vascular structures such as branches of the external carotid artery and the retromandibular vein.
Histologically, the gland is entirely serous and produces saliva rich in α-amylase, with a key role in the initial breakdown of carbohydrates, lubrication of the oral cavity and maintenance of oral homeostasis. Its secretion is regulated by the autonomic nervous system, mainly through parasympathetic fibers.
Its clinical significance is determined by its close connection with the facial nerve, which makes surgical interventions risky, as well as by the fact that the majority of salivary gland tumors arise in it. Additionally, the presence of intraorgan lymph nodes is important for the metastatic spread of neoplasms.
- How common are tumors in the parotid gland and what percentage of them are benign versus malignant?
- Salivary gland tumors are relatively rare, accounting for approximately 3-5% of neoplasms in the head and neck region, with approximately 70-80% of them arising in the parotid gland. According to data from modern epidemiological analyses, corresponding to the World Health Organization classification, approximately 75-85% of parotid tumors are benign and 15-25% are malignant. The most common benign tumors are pleomorphic adenoma and Wartin tumor. The probability of malignancy increases depending on the anatomical location of the gland, being lowest in the parotid, higher in the submandibular, and highest in the sublingual and minor salivary glands. Among malignant neoplasms, mucoepidermoid carcinoma is the most common (≈25-35%), followed by adenoid cystic carcinoma (≈15-20%) and acinic cell carcinoma (≈5-10%), with the distribution varying depending on the anatomical location and the population studied.
- Your publication discusses oncocytic papillary cystadenoma – How rare is this tumor and how does it differ from more common tumors?
- Oncocytic papillary cystadenoma is an extremely rare benign tumor of the salivary glands, occurring significantly less frequently than classical benign tumors. Data from retrospective series indicate that papillary cystadenomas constitute approximately less than 1% of all salivary gland tumors (e.g. 0.14% in a series of 700 cases). Even more limited is the proportion of the oncocytic variant, which is described as “extremely rare“, with mostly single or small case series available (e.g. publications with 2-3 patients). Only a limited number of cases of involvement of the major salivary glands have been reported in the literature (≈10 cases in separate reviews).
Due to this extreme rarity, knowledge of the tumor is based mainly on case reports and small series, which results in the lack of a systematic description of its imaging features. The available publications report only limited and nonspecific findings on CT and MRI, most often describing a well-demarcated cystic or multicystic lesion with papillary structures. The lack of a characteristic imaging profile leads to frequent preoperative diagnostic difficulties and confusion with more common tumors, such as Wartin's tumor (papillary cystadenoma lymphomatosum) or other cystic neoplasms.
Compared to the more common parotid tumors, oncocytic papillary cystadenoma is distinguished by:
-- extremely low incidence;
-- predominantly cystic architecture with papillary growths;
-- oncocytic cell differentiation without lymphoid stroma (unlike Wartin's tumor);
--lack of well-defined and validated imaging criteria.
- What are the most common symptoms that patients should see a doctor for if they suspect a problem in the parotid gland?
- The most common symptom of parotid gland involvement is the appearance of a painless, slowly growing mass in the parotid area, which is often the first and only sign of benign tumors. However, there are certain alarming symptoms that require prompt medical consultation.
These include:
-- pain or rapid increase in volume, which may indicate an inflammatory process or malignancy;
-- paresis or paralysis of the facial nerve, which is highly suspicious for a malignant process;
-- fixed, hard or poorly mobile formation;
-- skin changes or infiltration of surrounding tissues;
-- palpable cervical lymph nodes.
In summary, any newly appearing or progressive mass in the parotid region, especially if accompanied by neurological symptoms or pain, requires early evaluation by a specialist in order to exclude a neoplastic process.
- You describe specific imaging features in this rare tumor – How can they help doctors make a more accurate diagnosis before surgery?
- The specific imaging features we describe can significantly improve the preoperative diagnosis of this rare tumor. In our cases, multiparametric MRI demonstrated a recurring “triad” pattern: pronounced low signal („signal void“) on T2 and DWI, hyperintensity on T1 with fat suppression and lack of significant contrast enhancement of the cystic components, with enhancement limited to the papillary growths.
Interestingly, after comparing the imaging findings with the histological result, crystalloid inclusions were identified, which, together with the oncocytic cell component, probably underlie these unusual imaging features.
This combination is atypical for the more common parotid tumors and, recognized in an appropriate clinical context, may point to the diagnosis even before surgery.
This has direct clinical significance, as it allows for more confident planning of organ-preserving surgery that spares the facial nerve and avoids unnecessary aggressive treatment. However, it is important to emphasize that due to the extreme rarity of the tumor, these imaging features have not yet been validated in large series and should be interpreted with caution.
- How important is the assessment of the facial nerve in such cases and how does this affect the choice of surgical treatment?
- The assessment of the facial nerve is of key importance in tumors of the parotid gland, as it passes through its parenchyma and determines both the clinical picture and the surgical approach. Preoperative evaluation includes a clinical examination (for the presence of paresis or paralysis) and imaging methods that allow assessing whether the nerve is dislocated or there is evidence of infiltration. Preserved function usually points to a benign process, while neurological deficit raises the suspicion of malignancy.
This has a direct impact on the choice of surgical treatment:
-- in superficially located, probably benign lesions, partial (superficial) parotidectomy is performed with nerve sparing
-- in more extensive or deep tumors, total parotidectomy is required, and if possible the nerve is preserved
-- in proven infiltration by a malignant process, resection of the affected branches or the nerve itself may be required, with subsequent reconstruction
In this context, accurate preoperative assessment allows for an optimal balance between oncological radicalism and preservation of facial nerve function.
- What are the main challenges in the treatment of parotid gland tumors and what is the prognostic outcome for patients with timely diagnosis?
- Treatment of parotid tumors gland is challenging due to their histological heterogeneity and the complex anatomical relationships in the parotid region. The most important factor is the proximity of the facial nerve, which requires a precise balance between surgical radicality and preservation of its function.
The main challenges include:
-- difficult preoperative differential diagnosis, especially in rare or cystic tumors;
-- risk of facial nerve damage during surgical treatment;
-- wide variety of histological types, which complicates therapeutic management;
-- risk of recurrence, especially in incomplete resection or in some tumors such as pleomorphic adenoma.
As for prognosis, it is highly dependent on the histological type and stage of the disease. In benign tumors and timely surgical treatment, the prognosis is excellent, with a very low risk of recurrence. In malignant tumors, early diagnosis significantly improves survival, allowing radical treatment and better control of the disease. In summary, timely and accurate diagnosis is key to optimal outcome, allowing an individualized approach and maximum preservation of function with adequate oncological control.