Mucocele is defined as an accumulation and retention of mucus within a sinus as a result of an obstructed outlet. When the contents of the cavity are purulent in character, the condition is referred to as a "suppurating mucocele" or "pyocele."
Skillern1 set forth several criteria for differentiating mucoceles from pyoceles, which include the rate of growth, inflammatory symptoms, tenderness and consistency on palpation, severity of orbital symptoms, characteristics of the contents of the cyst, and the finding of pathogenic organisms on culture of this material. These criteria are useful in the typical case, but there are numerous borderline instances in which the foregoing criteria are of little aid in differential diagnosis.
When a low-grade pathogenic organism is involved in the development of a pyocele, the rate of cystic growth will not necessarily be appreciably more rapid than that of a mucocele; the patient may not exhibit any systemic