Type II collagen, but not aggrecan expression, distinguishes clear cell chondrosarcoma and chondroblastoma

Chondroblastoma and clear cell chondrosarcoma are uncommon skeletal neoplasms that have a strong tendency to involve the epiphysis of long bones. They also share some overlapping histological features. Thus, it can be difficult both radiographically and histologically to distinguish these neoplasms. So far there are no immunohistochemical markers available that have been shown to be helpful in differentiating these neoplasms.

In our study of a series of clear cell chondrosarcomas (n = 15) and chondroblastomas (n = 35), S100, vimentin, aggrecan and collagen type II were detected by immunohistochemistry.

We detected immunohistochemical evidence of type II collagen within both the extracellular matrix-rich (chondroid) and matrix-poor areas in all 15 cases of clear cell chondrosarcoma. In contrast, immunohistochemical analysis failed to show staining of collagen type II in any of the 35 chondroblastomas. Other markers, including S100 protein, vimentin and aggrecan proteoglycan were tested in parallel and found to be focally positive in both neoplasms.

Therefore, our data show that in cases when clear cell chondrosarcoma and chondroblastoma pose a diagnostic challenge, the presence of type II collagen in the extracellular tumour matrix significantly supports the diagnosis of clear cell chondrosarcoma and aids in distinguishing it from chondroblastoma.