The influence of site on the incidence and diagnosis of solitary central cartilage tumours of the femur. A 21st century perspective

Abstract

Objective: To determine the incidence of central cartilage tumours (CCTs) in the femur and the impact of site (proximal, mid and distal thirds) on tumour grade. To compare study results with historically published data.

Materials and methods: Retrospective review of solitary CCTs arising in the femur over the past 13 years. Data collected included location (proximal, mid and distal thirds) and final diagnosis in terms of tumour grade based on imaging features ± histology. Case material collected from three bone tumour textbooks provided historical data.

Results: 430 solitary CCTs were included in the femur. 73% cases arose in the distal, 3.7% in the mid and 23% in the proximal femur. The ratio of "benign" (combining enchondroma and atypical cartilaginous tumour (ACT)) to higher grade chondrosarcoma (CS) was 11:1 in the distal, 1:1 in the mid and 1:1.5 in the proximal femur, the distribution of benign to malignant tumours being significantly different between the regions (F test, p < 0.05). Comparison with historical data showed a reversal of the benign (enchondroma) to malignant (ACT and higher grade CS) of 30%:70%-84%:16% in the current series.

Conclusions: The site of origin of a CCT in the femur has an impact on final diagnosis with CS uncommon in the distal as compared with the mid and proximal femur. This is in contradistinction to historical data where the incidence of CS exceeded that of enchondroma at all sites.

Keywords: Central cartilage tumour; Femur; Solitary.

Fig. 1

Breakdown of current series by site and final diagnosis. Ench = enchondroma. ACT = atypical cartilaginous tumour. Gr 2 = grade 2 CS. Gd 3 = grade 3 CS. Dediff = dedifferentiated CS. CS = chondrosarcoma.

Fig. 2

48-year-old male with a 7 cm CCT of the distal femoral diaphysis. (a) sagittal T1-weighted and (b) axial proton density fat-suppressed MR images showing entrapment of fat within the tumour with no endosteal scalloping. Final diagnosis based on imaging alone was enchondroma. No documented disease progression over 7 years.

Fig. 3

42-year-old female CCT of the distal femoral diaphysis. (a) coronal STIR and (b) axial T1-weighted MR images showing a 7 cm in length lesion with focal endosteal scalloping. Needle biopsy did not show any overtly malignant features. Final consensus diagnosis based on imaging and histology was ACT. No documented disease progression over 8 years.

Fig. 4

49-year-old male with a CCT of the proximal femoral diaphysis. (a) sagittal STIR and (b) axial T2-weighted fat suppressed images showing cortical destruction with extra-osseous soft tissue extension. Imaging features suggested high grade CS probably dedifferentiated. Needle biopsy indicated grade 2 CS but the final histological diagnosis following surgical excision was dedifferentiated CS. The patient remains disease-free 18 months after surgery.

Fig. 5

Comparison of enchondroma to CS between current and historical data broken down by site within the femur. Ench = enchondroma. CS = chondrosarcoma including ACT formerly known as grade 1 CS.