Classification of frontal osteomas according to extension and implantation.

Table 1: Classification of frontal osteomas according to extension and implantation.

	Computed Tomography
GRADEI	Posterior inferior implantation in frontal recess Tumor medial to the lamina papyracea Anteroposterior diameter of the tumor is 75% of the anteroposterior diameter of the frontal recess
GRADEII	Anteroposterior diameter of the tumor is greater than 75% of the anteroposterior diameter of the frontal recess
GRADEIII	Implantation is anterior or superior in the frontal sinus Tumor extends lateral to the lamina papyracea
GRADEIV	The tumor occupies the entire frontal sinus