MICROSCOPIC DESCRIPTION:
The sections show a chondroid tumour. It forms sheets and focally with a lobulated architecture. The tumour is moderately cellular. The chondrocytes show nuclear enlargement, hyperchromasia, angulated nuclear contour and small nucleoli. Mitoses are inconspicuous. The background stroma is myxomatous with areas of necrosis. More mature chondroid matrix is also present. The tumour cells are S-100 and M2A positive. The Ki-67 index is less than 1%. They are CAM5.2 negative. The features are those of grade 2 chondrosarcoma.
DIAGNOSIS: Grade 2 chondrosarcoma.