Transition zone


Periosteal Reaction

Principal Features

The matrix of the lesion determines its plain radiographic appearance. Descriptive terms include Lytic, Sclerotic, Chondroid, Osteoid, Ground glass.

The transition zone describes the reaction with the underlying bone. Benign lesions are well defined (with or without a sclerotic margin). Increasing aggressiveness leads to a moth eaten or permeative pattern. These are divided by the size of the holes in the bone, permeative are less than 1mm.

The cortex may be expanded (benign) or breached or destroyed (malignant)

A periosteal reaction indicates extension through the cortex. Well defined continuous reactions are more likely to be benign, whereas discontinuous, spiculated or lamellated rractions are more likely to indicate aggression.