2007 OITE Question 18

Year	2007
Question Number	18
Category	Orthopaedic Disease

Question

18. A 50-year-old man has a painful, enlarging right hip mass as shown in Figure 5a. Which of the following pathology specimens shown in Figures 5b through 5f represents the malignancy that is most likely to arise in this condition?

1- Figure 5b
2- Figure 5c
3- Figure 5d
4- Figure 5e
5- Figure 5f

Figures

Answer (click for answer)

Preferred response: 5 – Figure 5f

The painful, enlarging hip mass in Fig 5a is likely the result of malignant transformation of an osteochondroma. Risk of malignant transformation into a chondrosarcoma is increased in hereditary multiple exostoses. Fig 5f pathology slide is most consistent with a chondrosarcoma, given the abundance of chondroid material (cf. Lackman tumor guide for changes seen with low- to high-grade cartilaginous lesions).
Many of the chondrosarcomas in this setting are low grade and can be treated successfully with wide excision. Patients with such lesions usually present with an expanding painful mass. Rarely, nerve compression is the presenting complaint. Ochsner et al (study cited in Stieber ref) found a mean age of 31 at diagnosis of malignancy, with malignant degeneration seldom occurring in the first decade or after the fifth decade of life. In adults, the presence of an osteochondroma with a cartilaginous cap >2 cm has been associated with an increased chance of malignancy.
2 genes have been associated with hereditary multiple exostoses: EXT1 and EXT2. Mutation of the EXT1 or EXT2 gene causes an error in the regulation of normal chondrocyte proliferation and maturation that result in abnormal bone growth.

Reference: Stieber JR, Dormans JP. Manifestations of hereditary multiple exostoses. J Am Acad Orthop Surg. 2005 Mar-Apr;13(2):110-20.