Enchondroma

Case contributed by Dr Patrick Baird-Fraser

Presentation

Right knee/hip pain, no history of trauma.

Patient Data

Age: 50 years
Gender: Male
X-ray

13cm chondroid lesion within the medulla of the distal femoral diametaphysis. No associated soft-tissue component, although partially imaged on the lateral projection.

MRI

Long 13.5x2.2x1.9cm (CCxTRxAP) heterogeneously intermediate T1 signal and heterogeneously high T2 signal lesion within the distal femoral diaphysis extending into the metaphysis. Evidence of minor endosteal scalloping affecting the posterior cortex of the femoral metaphysis.

Pathologist's Report

Bone biopsy from lesion in distal right femur. The specimen consist of three cores, the longest measuring 8mm, which are processed in one cassette and decalcified. 

Histology shows fragments of hyaline cartilage in which there is no significant increase in cellularity or cytological atypia. Fragments of cortical bone are also present. In one area cartilage is adjacent to bone. However there is no evidence of a permeative pattern or any overt features of malignancy.

The figures are consistent with enchondroma. There are no findings to suggest chondrosarcoma in this sample. 

Case Discussion

Differentiating between an enchondroma vs low-grade chondrosarcoma can be challenging 1.  Features that should raise suspicion of low-grade chondrosarcoma include a size over 5-6 cm, pain, and endosteal scalloping. Due to the size and pain, a biopsy was performed and histology confirmed an enchondroma

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