Nora lesion

 

Noras lesion 1Noras toe

 

Definition

 

Bizarre parosteal osteochondromatous proliferation 

 

Overgrowth of the periosteal surface

 

Epidemiology

 

Adults in their 20's and 30's

 

Males:Females  1:1

 

Site

 

Most common in the hands followed by the feet

 

Edoardo et al Acta Med Litu 2022

- systematic review of 322 cases

- 59% hands

- 19% feet

- femur / tibia / fibula

 

Natural history

 

Benign but locally aggressive

Grows rapidly

 

Clinical

 

Bony mass increasing in size over many weeks or a few months

 

X-ray

 

Well defined bony mass arising from the surface of the bone

- no medulla

 

Noras lesion 1Noras lesion 2

 

Noras lesion 3Nora's lesion 4

 

CT

 

Lesion not continuous with adjacent with cortex

- no medulla

- no cartilage cap

 

MRI

 

Typical tumour picture (high SI on T2 / low SI on T1)

 

No cartilage cap

No periosteal reaction

 

DDx

 

Osteochondromas

- cortex and medullary cavity is continuous with the cortex and medullary cavity of the lesion

 

Myositis ossificans

 

Parosteal osteosarcoma / chondrosarcoma

 

Pathology

 

Gross 

- nodular surface covered with glistening cartilage 

- bone in the lesion has a distinct blue tint

 

Histology

 

Mix of cartilage, bone and fibroblasts

- cartilage hypercellular and chondrocytes enlarged

 

Management

 

Wide excision

 

Recurrence

 

Edoardo et al Acta Med Litu 2022

- systematic review of 322 cases

- surgical excision in 273

- recurrence rate of 37% (102/273)