Osteochondroma in laboratory rats. A report of 3 casesin a Fischer-344, a Sprague Dawley, and a Wistar rat. Brief communication

Three cases of osteochondroma in a male Sprague-Dawley(SD) rat, a female Fischer (F344) rat, and a male Wistar rat are described. The rats were aged between 26 and 30 months. All osteochondromas were considered to beof spontaneous origin. The Wistar rat had multiple osteochondromas on both hind legs, the skull base, and a lumbar vertebra, whereas each of the F344 and SD rats was affected by a solitary osteochondroma, also on a lumbar vertebra. The lumbar osteochondromas were similar in appearance in all rats and consisted of a centralcore of trabecular bone, interspersed with fatty marrow and covered by a cap of hyaline cartilage. The additional tumors in the Wistar rat represented different developmental stages of osteochondroma with or without endochondral activity. The osteochondromas in the ratswere morphologically similar to those described in humans and some domestic animal species.