Final answer:
The nurse should expect a positive muscle biopsy result for a patient with polymyositis, showing muscle degeneration and inflammation.
Step-by-step explanation:
The nurse should expect a positive muscle biopsy result for a patient with polymyositis. Polymyositis is an inflammatory muscle disease that affects the muscles, causing weakness and inflammation. A muscle biopsy is a definitive diagnostic test that involves removing a small piece of muscle tissue for examination under a microscope. In polymyositis, the biopsy will typically show muscle degeneration and inflammation.