Several techniques have been developed, such as query expansion, cluster-based retrieval and dimensionality reduction to resolve low search precision and low search recall issues. Of these techniques, this paper proposed cluster-based query expansion using language modeling. Through our experiments in TREC genomic track ad-hoc retrieval task, we explore and demonstrate clusters that are created based on the whole collection or the initially returned document results of the original query can be utilized to perform query expansion and eventually improve the overall effectiveness and performance of information retrieval system in the biomedical domain.