Rare forms of chondroblastoma. Cystic and diaphyseal types.

The authors describe 4 cases of cystic chondroblastoma, three located in the epiphysis and one in the diaphysis. In 2 cases, the tumour macroscopically resembled a simple bone cyst and the tumour tissue consisted of small collections of cells lining the cystic cavity, which was devoid of fluid contents. In the other 2 cases, the tumour macroscopically resembled an aneurysmal bone cyst, but the thin septi that separated the blood-filled lacunae consisted of chondroblastomatous tissue. In this variety of chondroblastoma, curettage of the cystic cavity must be particulary meticulous so as to avoid local recurrence should small islands of neoplastic tissue inadvertently be left behind.