Cranial chondrosarcoma in a paddlefish, Polyodon spathula (Walbaum)

Abstract. A large, focally extensive tumour was observed on the posterior aspect of the head of a 14 year-old paddlefish, Polyodon spathula (Walbaum), taken from Lake of the Ozarks, Missouri, USA. A morphologic diagnosis of chondrosarcoma was made based on the biology, radiographic examination and cellular anaplasia of the mass. The lack of attachment of the tumour of the axial skeleton suggests origin in the dermal bones characteristic of this species. This constitutes the first record of a tumour with these characteristics from cartilaginous non-elasmobranch or elasmobranch fishes.