You will be shown biomedical passages and your task is to the answer the provided question. Provide a concise and accurate response and do not include any additional text in the response other than the answer.

Question: How many genes are screened by the FoundationOne companion diagnostic?

Context: In this study, we analyzed the clinicopathologic characteristics and comprehensive genomic profiling of 18 patients with pure triple-negative apocrine carcinomas (TNACs) using a 324-gene panel assay (FoundationOne CDx).
324