On my weekly visit to a research laboratory, I encountered a 14-month-old dog with lameness in its left hind limb. The dog is one of a small colony of male beagles, aged between 1 and 3 years ...

The mouse had a raised, ulcerated mass on the flank of its right hind limb that measured 2.0 cm × 2.5 cm (Fig. 1). The lesion was first observed 15 d previously and had grown rapidly ...