Defining Large Maxillary Sinus Polyps
There is no universally established size threshold that defines a "large" maxillary sinus polyp in the medical literature, as the term is used descriptively rather than as a standardized classification. However, clinical context and functional impact guide management decisions more than arbitrary size cutoffs.
Clinical Context for Size Assessment
The available evidence addresses polyp size primarily in relation to functional consequences rather than absolute measurements:
Mucous retention cysts (a specific type of maxillary sinus lesion) are considered clinically significant when they occupy two-thirds or more of the sinus volume, as this may block natural sinus drainage 1
Mucosal cysts that do not interfere with sinus elevation procedures and maintain a patent osteomeatal complex are not considered problematic regardless of size 2, 3
The critical factor is whether the lesion impacts the natural ostium or blocks mucosal drainage, not the absolute size measurement 3
Distinguishing Polyps from Cysts
Understanding the distinction is essential for proper classification 2:
Polyps tend to be pedunculated and arise from the sinus walls, with antrochoanal polyps specifically originating from maxillary sinus mucosa and extending through ostia toward the choana 4, 5
Mucous retention cysts are typically dome-shaped, originate from the sinus floor, and contain yellow serous fluid 3
Both can vary considerably in size, from small incidental findings to lesions that fill the entire antrum 6
Functional Assessment Over Size
The most clinically relevant assessment focuses on functional impact rather than dimensional measurements 2, 7:
Evaluate whether the osteomeatal complex remains patent on CT imaging 7, 1
Determine if the lesion causes complete or partial sinus radiopacity 2
Assess for bone erosion or expansion, which suggests more aggressive pathology requiring different management 2
Practical Clinical Thresholds
While not specifically defining "large," the evidence provides these actionable thresholds:
Mucosal thickening >4mm warrants ENT referral before dental procedures 7
Lesions causing complete sinus radiopacity suggest chronic rhinosinusitis with polyps and require ENT evaluation 2, 7
Polyps that are large enough to cause choking or extend into the nasopharynx represent extreme cases requiring urgent intervention 8
Key Clinical Pitfall
Do not confuse Schneiderian membrane thickness (relevant during sinus lift procedures) with mucosal thickening or polyp size visible on CT imaging 7. These represent different anatomical structures and clinical contexts. The membrane itself is thin (typically measured in micrometers during surgery), while pathologic mucosal thickening and polyps are measured in millimeters to centimeters.