Case contributed by Dr Henry Knipe


Lump on knee.

Patient Data

Age: 20 years
Gender: Female

In the right proximal tibia, there is a sessile posterolateral ossesous mass continuous with the medullary cavity with saucerising of the proximal fibula.


Osseous lesion arising from the proximal tibial shaft with broad attachment. Cartilage cap measures up to 1 cm in thickness. Saucerisation of the fibular neck is again noted. 


MACROSCOPIC DESCRIPTION: A segment of bone with a base measuring 55 mm in length x 22 mm in diameter with a protuberant pale white glistening tumour nodule 35x30x up to 32 mm in thickness. Base inked blue. Sectioning reveals a cartilage cap up to 10 mm in thickness. 

MICROSCOPIC DESCRIPTION: Sections show an osteochondroma composed of lamella bone forming a short, broad stalk covered by a 1 cm cartilaginous cap consisting of hyaline cartilage. Chondrocytes demonstrate endochondral ossification with normal growth maturation. No chondrocyte hypercellularity, atypia, mitoses or necrosis are seen. There is no invasion of bone or adjacent soft tissues. There is no evidence of malignancy.

DIAGNOSIS: Osteochondroma.

Case Discussion

Imaging findings are typical of a sessile osteochondroma. Features of malignant transformation (which are absent in this case) usually occur in the cartilage cap and include:

  • cartilage cap >1.5 cm
  • growth after skeletal maturity
  • pain
  • frankly malignant features such as cortical destruction, soft tissue mass, and new lucency
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Case information

rID: 46016
Published: 17th Jun 2016
Last edited: 28th Oct 2019
Inclusion in quiz mode: Included

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