Branchial osteogenetic neoplasm in barbel Barbus barbus plebejus

A branchial osteogenetic neoplasm affecting a barbel Barbus barbus plebejus (Valenciennes, 1829) is described. The osteoblasts' pleomorphism, the lack of a well-developed and complete separation, the presence of eccentric, te rminal proliferative edges infiltrating the lining tissues and the abundant tumour matrix suggest a histopathological diagnosis of a 'productive osteo blastic osteosarcoma'. The occurrence of eosinophilic granule cells (EGCs) scattered among neoplastic tissue is discussed in relation to the neoplasti c growth and the inflammatory reaction, with reference to recent discoverie s in mammalian mast cell biology.