Table 1. The Fisch-Mattox and Glasscock-Jackson classification system of glomus tympanicum tumor

The Fisch-Mattox classification system
Grade	Definition
A	Tumor entirely within the middle ear space
B	Tumor only within the middle ear or mastoid portion of the temporal bone
C	Tumor within the infralabyrinthine temporal bone or petrous apex
D1	Tumors with <2 cm of intracranial extension
D2	Tumors with ≥2 cm of intracranial extension

Glasscock-Jackson classification system
Type	Description
I	Small mass limited to the promontory of the middle ear
II	Tumor completely filling the middle ear cleft
III	Tumor within the middle ear and mastoid extension
IV	Tumor within the middle ear and mastoid with extension into the external auditory canal