Maxillary sinus cyst: symptoms, diagnosis, treatment

A maxillary sinus cyst is a benign, mucus- or serous-filled lesion that forms in the maxillary sinus cavity and is most often detected incidentally during computed tomography (CT) or cone-beam CT scanning. The most common type is a mucous retention cyst, which occurs due to a blockage in the excretory duct of the mucous gland. Unlike a mucocele, a classic retention cyst is not expansive and rarely leads to bone destruction. [1]

Most retention cysts are asymptomatic. Symptoms develop when the sinus ostium becomes obstructed, inflammation occurs, or when associated with odontogenic (dental) pathology. In such cases, patients may complain of nasal congestion, facial pain localized to the cheek, discomfort when tilting the head, and dental symptoms involving the upper premolars and molars. [2]

Diagnosis is usually made instrumentally. The method of choice for initial evaluation is computed tomography of the paranasal sinuses, and for detailed dental assessment, cone-beam computed tomography (CBCT) is used. Magnetic resonance imaging (MRI) helps differentiate fluid-filled lesions from soft tissue polyps and assess complications. Treatment options are individualized, ranging from observation in the absence of symptoms to endoscopic intervention for complaints, obstruction, or an odontogenic source. [3]

In recent years, surgical approaches have become more organ-preserving. Functional endoscopic sinus surgery allows for cyst removal through the natural opening with a low risk of complications and rare recurrences. For odontogenic cases, combined treatment by an otolaryngologist and dentist in a single visit is considered optimal, reducing the frequency of recurrent episodes of inflammation. [4]

Code according to the International Classification of Diseases, 10th and 11th revisions

In the International Classification of Diseases, Tenth Revision, cysts and mucoceles of the nose and paranasal sinuses are coded under section J34.1. This code is used for cysts of any paranasal sinus, including the maxillary sinus, and for mucoceles when the lesion expands expansively into the sinus. In routine documentation, the code is supplemented with the location and clinical details, such as odontogenic origin or the presence of complications. [5]

The International Classification of Diseases, Eleventh Revision, uses the code CA0C for cysts or mucoceles of the nose and paranasal sinuses. This code covers cysts of all sinuses, including the maxillary sinus, and mucoceles, as well as variants with more detailed anatomical details. In cases of concomitant odontogenic infection, additional coding for the disease of the dentoalveolar region is used according to the rules of post-coordination. [6]

Table 1. Coding examples

Clinical situation	International Classification of Diseases 10	International Classification of Diseases 11
Retention cyst of the maxillary sinus	J34.1	CA0C
Mucocele of the maxillary sinus	J34.1	CA0C
Cyst in odontogenic sinusitis	J34.1 + code for causal odontogenic pathology	CA0C + post-coordination for odontogenic disease
The choice of codes is specified according to local rules and the clinical formulation of the diagnosis. [7]

Epidemiology

Retention cysts are one of the most common incidental findings in the maxillary sinus. In studies using cone-beam computed tomography, the incidence of such findings ranges from 10-13% of all sinuses examined, highlighting their prevalence in general dental practice. Results are influenced by the population and indications for examination. [8]

In some studies, the incidence of retention cysts was 4.9%, with a predominance of lesions in the right maxillary sinus. The variability in these values is explained by differences in selection criteria, age groups, and imaging methods. It is important to interpret such findings based on clinical findings, not just their presence on imaging. [9]

When analyzing the entire spectrum of maxillary sinus pathologies using cone-beam computed tomography, changes are detected in up to 45.8% of cases, of which retention cysts account for approximately 12.3%. These data confirm that cysts are a common, but not the only, cause of changes in images. [10]

Mucoceles of the maxillary sinus are significantly less common than retention cysts, but are of greater clinical significance due to their expansive growth and the risk of complications. Endoscopic surgery, with favorable long-term results, is the treatment of choice for mucoceles. [11]

Table 2. Estimated prevalence rates

Source and method	Pathology	Frequency
Cone beam computed tomography, retrospective analysis	Any changes in the maxillary sinus	45.8% of cases; of which retention cysts 12.3%
Observation series	Retention cysts	4.9%
Clinical series	Mucocele of the maxillary sinus	Rarely, in single percentages among patients with mucocele
[12]

Reasons

The primary mechanism for the formation of a retention cyst is a blockage of the mucous gland's excretory duct in the sinus wall, leading to the accumulation of secretions and the formation of a rounded cavity under the mucous membrane. This process typically does not lead to bone destruction and remains asymptomatic for a long time. [13]

Cysts often accompany chronic mucosal inflammation, allergic rhinitis, and anatomical variations that impede ventilation and drainage. Impaired mucociliary clearance maintains stagnation of contents and increases the risk of symptoms as the cyst enlarges. [14]

A separate and important group of causes are odontogenic factors. Infections of the roots of the upper teeth, perforations of the sinus floor during implantation, sinus lifts, and jaw cysts can involve the maxillary sinus and lead to persistent inflammation, in which case the retention cyst becomes clinically significant. Proper management requires collaboration between an otolaryngologist and a dentist. [15]

A mucocele, unlike a retention cyst, forms as a curtain of isolated mucosal tissue with long-term obstruction, causing sinus dilation and sometimes destruction of the thin bony walls. Causes include chronic infection, trauma, and previous surgery. This condition requires surgical treatment. [16]

Table 3. Comparison of retention cyst and mucocele

Sign	Retention cyst	Mucocele
Pathogenesis	Blockage of the gland's excretory duct	Long-term obstruction of the sinus segment
Height	Non-expansive	Expansive, with bone remodeling
Symptoms	Often absent	Often pronounced, with pressure and deformation
Tactics	Observation or sparing endoscopy for symptoms	Compulsory endoscopic surgery
[17]

Risk factors

Anatomical factors that impair ventilation and drainage increase the likelihood of symptomatic progression: deviated nasal septum, narrowing of the middle meatus, variations in the uncinate process, and lateralization of the middle turbinate. These features mechanically impede outflow and may contribute to inflammation. [18]

Dental interventions and dental pathologies in the maxilla—implantation, sinus lift, chronic periapical changes—increase the risk of persistent sinusitis. Recent reviews emphasize that up to 10-40% of chronic unilateral sinusitis cases are odontogenic in origin. This requires screening for the underlying cause before choosing a treatment strategy. [19]

Previous sinus surgeries and trauma alter the anatomy of the sinus ostium and can lead to isolated pockets where mucoceles form. In such cases, facial asymmetry, pain, or respiratory distress develop over the years, making surgery unavoidable. [20]

Allergic and inflammatory conditions of the mucous membrane promote hypersecretion and swelling, which contributes to the blockage of glandular ducts. Against this background, even a small cyst can become symptomatic with accompanying swelling of the sinus orifice. [21]

Table 4. Risk situations and preventive hints

Factor	Potential effect	What to consider
Deviated septum, narrow middle passage	Drainage obstruction	Correction of anatomy according to indications
Implantation, sinus lift	Odontogenic sinusitis	Preoperative evaluation of sinuses and teeth
Previous sinus surgery	Isolated pockets, mucoceles	Early diagnosis of new symptoms
Allergic rhinitis	Chronic inflammation of the mucous membrane	Allergy control, topical therapy
[22]

Pathogenesis

A retention cyst forms submucosally, with a wall consisting of thinned mucosa and a lost ductal patency. Its contents are mucus, which the gland continues to produce. On computed tomography, this formation appears as a dome-shaped protrusion of the sinus wall with a clear outline and uniform density. [23]

With odontogenic involvement, inflammation spreads from a focus at the root apices, through the thin sinus floor, or through perforation during implantation. This maintains chronic mucosal edema, impairs ventilation, and promotes cyst growth and secondary sinusitis. Without sanitation of the dental lesion, a lasting treatment effect is difficult to achieve. [24]

A mucocele occurs due to long-term obstruction and accumulated secretions, which cause pressure on the bony walls and their remodeling. On CT and MRI, a mucocele shows signs of sinus dilation and bone thinning, and when infected, it develops into a mucopyocele. This condition carries a risk of complications and requires surgery. [25]

A comprehensive radiological approach emphasizes the single mechanism—an imbalance between secretion formation and drainage. Any factor that chronically impedes drainage increases the likelihood of symptomatic progression and complications. This explains why cysts remain asymptomatic for years in some patients, while in others they lead to complaints and surgery. [26]

Symptoms

Most retention cysts are asymptomatic and are discovered incidentally during dental or otolaryngological examinations. The patient may not notice any problems until the cyst reaches a size that interferes with sinus ventilation or until inflammation occurs. This is an important argument for careful monitoring. [27]

When a cyst becomes symptomatic, the most common symptoms are a feeling of pressure in the cheek, unilateral nasal congestion, postnasal drip, and increased discomfort when tilting the head. Dull pain and hypersensitivity of the maxillary teeth sometimes occur. In such cases, the cyst serves as a marker of impaired sinus drainage. [28]

With a mucocele, symptoms are more pronounced: increasing distension, sinus wall deformation, soft tissue swelling, and the risk of complications. Infection can cause purulent discharge, fever, and severe pain. Such cases require immediate evaluation for surgical planning. [29]

If the cyst is associated with an odontogenic source, dental complaints may also occur: pain upon percussion, a feeling of fullness in the upper molars, and bad breath associated with persistent sinusitis. These signs suggest the need for a joint examination by a dentist and otolaryngologist. [30]

Classification, forms and stages

Clinically, a distinction is made between retention cysts, mucoceles, and cysts associated with odontogenic pathology. A retention cyst is non-expansive, a mucocele is expansive and potentially destructive, and cysts associated with odontogenic sinusitis accompany the inflammatory process and require debridement of the dental lesion. This distinction is important because treatment strategies differ. [31]

There is no standardized staging for a retention cyst. For a mucocele, the staging is based on its extent, involvement of the bony walls, proximity to the orbit, and the presence of infection. These parameters determine the urgency of intervention and the extent of endoscopic surgery. [32]

Cysts are considered separately in the context of future dental procedures. Before sinus lifting and implantation, the presence of a large cyst requires a discussion of the treatment timing and sequence of procedures to reduce the risk of sinusitis and swelling after surgery. [33]

In groups with a high probability of an odontogenic source, the cyst is only part of the problem. Here, the classification is based on odontogenic maxilloantral pathology, and the solution involves simultaneous removal of the dental lesion and restoration of sinus drainage. [34]

Complications and consequences

The main risks of a retention cyst are related to impaired ventilation and secondary inflammation. This can lead to unilateral chronic sinusitis, deteriorating quality of life, and increased need for antibiotics. Early assessment helps prevent a protracted course. [35]

Mucoceles carry the risk of bone remodeling and thinning of the sinus walls, and as they progress, they can involve the orbit and soft tissues of the face. In the infected form—mucopyocele—the risk of severe inflammatory complications increases. Surgical treatment in such situations is the standard. [36]

In cases of odontogenic origin, chronic inflammation persists without treatment of the underlying tooth or implant, leading to recurrence of symptoms after isolated sinus surgery. A combined approach by an otolaryngologist and dentist improves outcomes. [37]

Rare but reported complications include persistent facial pain and postprocedural complications if the approach is chosen incorrectly. Modern endoscopic approaches minimize these risks with adequate planning and visualization. [38]

When to see a doctor

You should seek medical attention if you experience persistent unilateral nasal congestion, facial pain, or pressure in the cheek area for more than 2-3 weeks, especially if symptoms worsen when tilting your head. These symptoms may indicate a drainage problem in the maxillary sinus and require examination. [39]

Urgent consultation is necessary in cases of severe pain, fever, purulent discharge, or facial swelling, which may indicate an infected cyst or acute sinusitis. Delay in this case increases the risk of complications and prolongs treatment. [40]

If implantation or sinus lift surgery is planned and a cyst is detected on imaging, it is necessary to discuss the procedure with an otolaryngologist and dentist in advance. This will minimize the risk of inflammation and ensure the stability of the future implant. [41]

Patients who have undergone sinus surgery should seek medical attention if new distension or deformity develops, as this may be a mucocele years after the procedure. Endoscopic evaluation is mandatory in such cases. [42]

Diagnostics

Step 1. Collection of complaints and examination. Focus on unilateral symptoms, dental complaints, and those associated with head tilt. Nasal endoscopy allows for assessment of the middle nasal meatus, swelling, and the presence of pus, as well as orientation to the anatomy of the anastomosis. [43]

Step 2. Basic imaging. CT scanning of the paranasal sinuses is the standard for assessing cyst size, the condition of the anastomosis, and the bony walls. In dental practice, cone-beam CT scanning is used to evaluate the sinus floor, tooth roots, and implants. [44]

Step 3. Clarifying imaging. Magnetic resonance imaging can help differentiate a cyst from a polyp and identify complications, especially if a mucocele or mucopyocele is suspected. Contrast is usually not required. [45]

Step 4. Search for the odontogenic source. Examination by a dentist, targeted dental x-rays, assessment of implants and root apices. If the source is confirmed, a single-stage treatment plan is planned. [46]

Step 5. Laboratory and severity criteria. General clinical tests are used if signs of infection are present. Indications for urgent referral include severe facial swelling, fever, severe pain, and suspected complications. [47]

Table 5. Diagnostic roadmap

Target	Method	What does it give to the clinician?
Confirm the presence of a cyst	Computed tomography or cone beam computed tomography	Size, location, condition of the anastomosis
Distinguish between a cyst, a polyp, and soft tissue formations	Magnetic resonance imaging	Signal characteristics, complications
Identify the odontogenic source	Dental examination, targeted x-rays	Tactics for sanitation of the outbreak
Assess the need for urgency	Clinic, general clinical tests	Signs of infection or complications
[48]

Differential diagnosis

An antrochoanal polyp differs from a cyst in that it is a soft tissue formation originating from the sinus and extending into the nasal cavity and choana. Computed tomography and endoscopy show the polyp's tract, often with obstruction, whereas a cyst protrudes dome-shaped from the wall and remains within the sinus. [49]

A fungal mass in the maxillary sinus and chronic hyperplastic mucosa can mimic a cyst on cone-beam computed tomography. In such cases, magnetic resonance imaging and densitometry analysis help clarify the nature of the process and avoid unnecessary surgery. [50]

Odontogenic cysts of the jaw that contact the sinus floor require careful dental examination. Unlike sinus retention cysts, these are maxillary bone cysts, and management focuses on their removal and subsequent restoration of sinus drainage if necessary. [51]

Mucoceles are distinguished by signs of bone expansion and thinning, sometimes with deformation of the walls and involvement of the orbit. Infection leads to mucopyocele development, which carries the risk of severe complications and requires immediate surgical treatment. [52]

Treatment

Observation is appropriate for asymptomatic retention cysts with no signs of drainage obstruction and no odontogenic lesion. In such cases, dynamic observation with periodic endoscopy and imaging monitoring is recommended if new complaints arise. This approach avoids unnecessary surgery in most patients. [53]

If symptoms associated with sinus ventilation are present, the first steps are anti-inflammatory measures: irrigation with isotonic solutions, local anti-inflammatory agents as indicated, and treatment of allergic rhinitis. Drug therapy does not "resolve" the cyst, but reducing swelling of the sinus opening often reduces the severity of symptoms. The decision to perform surgery is based on a combination of symptoms and imaging data. [54]

If an odontogenic source is identified, the basic strategy is combined sanitation. The best results are demonstrated with a single-stage procedure: functional endoscopic sinus surgery to restore drainage and simultaneous removal of the causative dental lesion. This tactic reduces recurrence and ensures highly effective treatment. [55]

The gold standard for surgical treatment of symptomatic retention cysts and mucoceles is an endoscopic approach through the natural ostium with widening of the middle nasal meatus. This method is characterized by a low rate of complications and recurrence, a short hospital stay, and rapid recovery. Historically, external approaches are used rarely, for specific indications. [56]

The choice of endoscopic route depends on the location of the cyst. For locations near the medial or superior nasal wall, a mid-nasal approach is sufficient. For difficult-to-reach lateral and anterior regions, a pre-lacrimal approach is used, and for extensive lateral spread, a canine fossa approach with endoscopic assistance is used. These approaches enhance visualization while maintaining minimal trauma. [57]

Mucoceles require comprehensive surgery with the creation of a stable drainage system. Endoscopic marsupialization produces good long-term results, with rare recurrences. In cases of mucopiocele, surgical drainage and antibiotic therapy are added as clinically indicated. External interventions are reserved for situations where endoscopic revision is not possible. [58]

In a dental context, planning is important before sinus lift and implantation. For large cysts, removal of the lesion before bone grafting is considered, sometimes with a delay of several months to stabilize the mucosa. Literature data suggests different approaches, so the decision is made individually, taking into account the extent of the planned reconstruction. [59]

Postoperative care includes nasal irrigation, topical anti-inflammatory medications as indicated, endoscopic monitoring, and patient care training. It is important to ensure patency of the anastomosis during the first few weeks and prevent crust formation. If the process is odontogenic, dental supervision is essential. [60]

Indications for urgent postoperative evaluation include increasing pain, fever, unilateral facial swelling, bleeding, or a sharp increase in congestion. Early intervention prevents complications and reduces the risk of reoperation. The long-term prognosis is favorable with proper access and elimination of causative factors. [61]

Table 6. Indications for treatment and choice of method

Scenario	Tactics	Comment
Asymptomatic retention cyst	Observation	Monitoring when symptoms appear
Symptomatic cyst without odontogenic source	Endoscopic removal through a natural anastomosis	Low risk of complications and relapses
Cyst with odontogenic source	One-stage functional endoscopic sinus surgery plus sanitation of the dental and maxillary lesion	High efficiency and low relapse rate
Mucocele or mucopiocele	Endoscopic marsupialization and drainage, antibacterial therapy as indicated	Mandatory surgical treatment
[62]

Prevention

Prevention of symptomatic progression is associated with risk factor management. Control of allergic inflammation, nasal hygiene during exacerbations, timely treatment of rhinosinusitis, and correction of significant anatomical obstructions as indicated are important. This reduces the likelihood of drainage impairment and secondary inflammation. [63]

Before implantation and sinus lift, planning is required based on computed tomography or cone-beam computed tomography, assessment of the mucosa and sinus floor, and debridement of chronic lesions. If a large cyst is detected, reconstruction may be postponed until the mucosa stabilizes after endoscopic treatment. [64]

Patients who have undergone sinus surgery benefit from follow-up examinations and education about the early signs of drainage problems. This allows for the early detection of mucoceles, which can develop years later. [65]

If signs of odontogenic inflammation are present, an early consultation with a dentist is indicated. A combined approach prevents prolonged recurrences of sinusitis and reduces the need for repeat surgeries. [66]

Table 7. Preventive steps before dental procedures

Stage	Action	Target
Preoperative screening	Computed tomography or cone beam computed tomography of the sinuses	Evaluation of the mucosa and anatomy
Sanitation of the outbreak	Treatment of periapical processes, revision of implants	Eliminating the source of inflammation
For a large cyst	Endoscopic treatment before reconstruction	Reducing the risk of sinusitis
Joint planning	Team otorhinolaryngologist plus dentist	Minimizing relapses
[67]

Forecast

For asymptomatic retention cysts, the prognosis is favorable: many remain stable for years and require no intervention. When symptoms occur, endoscopic treatment is effective and has a low recurrence rate with proper postoperative follow-up. [68]

Mucoceles have an excellent prognosis after endoscopic marsupialization with the creation of a stable drainage system. Long-term series demonstrate favorable outcomes and a low regrowth rate. Timely recognition and targeted treatment are essential. [69]

In cases of odontogenic origin, the outcome directly depends on the treatment of the underlying cause. Single-stage combined interventions shorten treatment time and reduce the likelihood of recurrent episodes of sinusitis. [70]

In rare cases of unfavorable anatomy and associated pathology, extended endoscopic approaches may be required. Even in these situations, organ-preserving methods provide good functional results. [71]

Answers to frequently asked questions

Should any maxillary sinus cyst be removed immediately after detection on imaging? No. Asymptomatic retention cysts are usually observed, and the decision to operate is made based on complaints, drainage obstruction, or an odontogenic source. [72]

What's the difference between a cyst and a mucocele, and why is this important? A retention cyst is non-expansive and rarely destroys bone, whereas a mucocele widens the sinus and can thin the walls. A mucocele requires surgery, while a cyst often requires observation. [73]

Do medications help "dissolve" a cyst? No. Medications reduce swelling and inflammation, but do not eliminate the cyst wall. If symptoms persist and drainage is impaired, endoscopic methods are crucial. [74]

What should you do if a cyst is detected before implantation or sinus lift? Discuss the strategy with your team: it is often advisable to endoscopically remove the cyst and stabilize the mucosa, and then plan reconstruction. Sometimes this is performed in a single stage, provided safety precautions are met. [75]

How safe is endoscopic surgery? Endoscopic interventions on the maxillary sinus have a low risk of complications and rare recurrences with proper access and postoperative monitoring. [76]