Examples relate to integrating and extracting topics from content of heterogeneous sources. Observed words are identified in documents, which are received from the heterogeneous sources. Next, document metadata and source metadata are obtained from the heterogeneous sources. The document metadata is used to calculate word topic probabilities for the observed words, and the source metadata is used to calculate source topic probabilities for the observed words. A latent topic is then determined for one of the documents based on the observed words, the word topic probabilities, and the source topic probabilities.