A 65-year-old woman presents with a brain mass and proximal muscle weakness. Which condition is most likely affecting her?

The patient’s presentation of a brain mass along with proximal muscle weakness suggests a specific underlying condition. In this case, the likely scenario here is the presence of a brain metastasis, particularly related to the history of small cell carcinoma, which can commonly spread to the brain and manifest with neurologic symptoms.

Small cell lung cancer (SCLC), also known as small cell carcinoma, is known for its aggressive nature and tendency to metastasize to the brain. Patients with small cell carcinoma can develop neurological symptoms due to the metastasis of cancer cells to the central nervous system. The muscular weakness observed is likely related to a paraneoplastic syndrome linked to SCLC, which can affect muscle strength and function.

The age of the patient, the presence of a brain mass, and the proximal muscle weakness aligns well with this diagnosis. The specific symptoms of weakness, particularly proximal, suggests a process that might include muscular involvement or paraneoplastic syndromes common with this type of malignancy.

In contrast, the other options listed either do not commonly lead to brain metastasis or do not typically present with the same symptoms. Anaplastic ependymoma, while it can cause a brain mass, is more likely to cause other types of symptoms related to the location