[A rare tumor of the knee joint].

The tumour in a male of 62 consisted of vesicular vacuolized cells in a myxomatous substance. References are given as to the morphological similarity between chondrosarcoma and so-called chordoid-sarcoma. At the light and electron microscopic level the signs of incomplete chondrogenesis are found, this permitting one to consider the tumour as a myxoid variant of chondrosarcoma.