Final answer:
An initial clinical assessment and further diagnostic tests like MRI scans are essential for a woman with a history of breast carcinoma presenting with decreased leg sensation and motor function to determine if it's due to metastatic disease or other conditions.
Step-by-step explanation:
When a 55-year-old woman, previously treated with a mastectomy for stage II breast carcinoma, presents with new onset decreased sensation and motor function in her right leg after five years, it is crucial to consider the possibility of metastatic disease or late complications of cancer treatment. The first step is to conduct a thorough clinical assessment, which would include a detailed neurological examination and history taking to determine the extent and progression of the symptoms. Further diagnostic tests such as MRI scans of the brain and spine, as well as blood work, might be needed to evaluate for potential metastasis to the central nervous system or other causes such as a spinal cord lesion or even non-neoplastic conditions like a stroke.