Review Question - QID 219537

This 37-year-old male with a past medical history of multiple hereditary exostosis (MHE) presents with left shoulder pain and radiographs showing a lytic lesion from a previous osteochondroma, which necessitated wide resection. This presentation is most likely consistent with secondary chondrosarcoma (Figure C/Answer 2).

Chondrosarcoma can be broadly categorized into primary or secondary, with the vast majority arising sporadically (primary). Secondary chondrosarcomas arise from a pre-existing benign cartilaginous lesion, namely osteochondromas or enchondromas, with the former accounting for the most cases (> 80%). While solitary osteochondromas have < 1% risk for malignant transformation, those with MHE are subjected to a higher risk for transformation at 5-10%. Moreover, central (pelvis, axial skeleton) osteochondromas have a higher tendency to undergo malignant transformation in comparison to their peripheral (appendicular skeleton) counterparts. Regardless, secondary chondrosarcomas arising from osteochondromas are typically low-grade, occurring in younger patients in their third or fourth decade of life. Chemotherapy and radiation are typically reserved for mesenchymal and dedifferentiated subtypes. As such, these lesions are treated with wide resection and reconstruction.

Kozawa et al. performed a multicenter retrospective review examining prognostic factors and survivorship in 81 Asian patients with dedifferentiated chondrosarcoma or high-grade (grade 3) chondrosarcoma. The authors noted the dedifferentiated subtype to have a worse prognosis, with 18.5% of patients being disease-free at five years (compared to 41.7% in grade 3). Stage and lack of treatment were prognostic for the dedifferentiated type, while age and lack of treatment were prognostic for high-grade chondrosarcoma. While chemotherapy did not affect survival, the authors concluded more studies examining chondrosarcoma patients in larger numbers are needed to better delineate chemotherapy's effect in high-grade and dedifferentiated chondrosarcoma.

Tsuda et al. performed a retrospective study evaluating survivorship and recurrence rates in 51 patients who experienced secondary chondrosarcoma arising from osteochondromas. The authors noted low-grade chondrosarcomas as the most common (69%), and 89.4% were disease-free at ten years following wide resection of their tumor. There was a 29% local recurrence rate, which was more common in chondrosarcomas of the pelvis. The authors ultimately recommend wide resection as the most appropriate treatment for secondary chondrosarcomas.

Figure A is an AP radiograph of the left shoulder demonstrating a lytic lesion arising from a previous osteochondroma. Figure B represents osteosarcoma. Figure C represents a low-grade chondrosarcoma, as exemplified by an abundance of cartilaginous matrix with several enlarged, binucleate chondrocytes. Figure D is a histological slide of Ewing's sarcoma. Figure E represents a histology slide of a benign enchondroma. Figure F is a histology slide of a malignant peripheral nerve sheath tumor.

Incorrect Answers:
Answer 1: This histological slide demonstrates cellular atypia with an abundance of osteoid matrix, consistent with osteosarcoma.
Answer 3: This histological slide shows sheets of round blue cells consistent with Ewing's sarcoma.
Answer 4: This histological slide reveals mature hyaline cartilage lobules separated by normal marrow, consistent with an enchondroma.
Answer 5: This histological slide shows spindle cells with wavy nuclei, consistent with a malignant peripheral nerve sheath tumor.