Enchondroma

Case contributed by Dr Bruno Di Muzio

Presentation

Incidental finding on radiograph.

Patient Data

Age: 45 years
Gender: Female

Left ankle radiographs

x_ray

There is a small eccentric geographic lytic lesion within the lateral aspect of the distal tibia, showing thin sharp sclerotic margins and punctate calcifications suggesting chondroid matrix. 

CT Left ankle

ct

In the posterolateral aspect of the distal left tibia, an eccentric cortically based lucent lesion is noted. This is not expansive. It has a benign appearance with mild cortical thinning. There are a few small opacities noted within it which may be fibrous or residual bone. No associated soft tissue mass, calcification or periosteal reaction is seen. 

CT-guided biopsy

ct

In consultation with the tumor surgeon, a route was chosen to transverse the extensor digitorum longus muscle. A Bonopty® kit was used, intravenous sedation, and local anesthesia. Two passes traversing the center of the lesion into the medulla on the other side. Bone and soft tissue cores in contiguity were obtained, placed in formalin. Biopsy track marked with sterile carbon up to the skin.

MRI - Targeted study

mri

The low-grade chondral lesion, abuts, mildly scallops the anterior and medial cortex of the distal tibial diaphysis, is unchanged in size. There is no extraosseous extension or periosteal reaction. Enhancement pattern is consistent with a low-grade lesion with no dedifferentiation detected. There is faint fascial thickening over extensor digitorum longus at the level of the tumor consistent with the biopsy path scarring, with no nodularity of this area seen. This lesion measures 12 mm in cross-section and 16 mm in length. No skip lesions are seen the rest of the tibia or the adjacent fibula. Longitudinal split tear of the peroneus brevis is noted. 

Case Discussion

MACROSCOPIC DESCRIPTION: "Left distal tibia bone biopsy": Three fragments of firm red tissue 2-4mm in maximum dimension received with a separate fragment of firm pale tan tissue 4mm in maximum dimension. A1.

MICROSCOPIC DESCRIPTION: The fragmented biopsies contain islands of cartilage, which appear to be surrounded by lamellar cortical bone. There is no invasion through the cortex. The chondrocytes show no significant nuclear atypia. Binucleated cells are absent. There are no mitoses or necrosis. Myxoid change is absent in the background. The overall features are consistent with an enchondroma. No evidence of malignancy is identified. Radiological correlation is recommended.

DIAGNOSIS: Left distal tibia: Features consistent with enchondroma.

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