What term is used to describe the focal smooth thinning of the inner margin of the bone, seen in this case on both x-ray and CT images of the femur? What does it imply?
Endosteal scalloping refers to the focal resorption of the inner margin of cortical bones, typically seen in long bones, due to slow growing medullary lesions. It is important to note that although it is usually evidence of a slow non-infiltrative lesion, it does not equate to benign aetiology and similar appearance can also be identified in myeloma and metastases. Some authors would prefer the term endosteal erosion for myeloma and metastases, as the underlying mechanism may well be different.
There is a lytic expansile mass in the intertrochanteric region of the left femur measuring 3.6 x 4.6 x 3.4 cm. There is endosteal scalloping of the cortex, with multiple intra-cortical lucencies within the proximal femur in keeping with cortical infiltration. At the anterior aspect of the femur, just medial to be greater trochanter there is complete loss of bone cortex in keeping with cortical breech/pathological fracture. There is soft tissue stranding surrounding the femur in this region.
The marrow of the imaged distal femur demonstrates multiple soft tissue masses in keeping with marrow infiltration.